ubuntu server to support unlimited or 100+ telnet users

Installation

You start by setting up a telnet server. This can be installed with

sudo apt-get install xinetd telnetd

Information about these package can be found here: xinetd telnetd

  Configuration

In /etc/inetd.conf there are configuration options (listed this one because it also has the option to set the amount of connections/users):

# Simple configuration file for xinetd
#
# Some defaults, and include /etc/xinetd.d/
defaults
{
# Please note that you need a log_type line to be able to use log_on_success
# and log_on_failure. The default is the following :
# log_type = SYSLOG daemon info
instances = 60
log_type = SYSLOG authpriv
log_on_success = HOST PID
log_on_failure = HOST
cps = 25 30
}

instances is the number of connections and unlimited can be used instead of a number.
There is also /etc/services where you can change the port number where telnet should listen too.
And there is /etc/xinetd.d/telnet where you can set up IP ranges that are allowed (only_from =) or disallowed (no_access =) access and also access time (access_times =).

  (Re-)starting telnet service

To apply changes you then need to restart services with

sudo /etc/init.d/xinetd restart

  -- Warning --

  Telnet is fast but also insecure. It sends all your text, including your password, in plain text that can be read by anyone with the right tools. SSH, on the other hand, encrypts all your communication and so is more resource-intensive but secure even a government security agency sniffing your packets for some reason would still have a hard time cracking the encryption. If you are looking for SSH server configuration in Ubuntu check here.


How to downgrade Java version 1.6.0_36 to 1.6

Ok, I guess the issue is not the Java version itself but rather the used JDK. This Stack Overflow answer suggests that older Android versions require the Oracle JDK to build. Reading between the lines of the “Installing the JDK” section of the official Android source documentation suggests the same: “To develop older versions of Android, download and install the corresponding version of the Java JDK” – note the link to the Oracle website at the end … that could have been made clearer.

So, in essence you should get the Oracle JDK and make sure that your build uses that instead of the OpenJDK you currently use. This other Stack Overflow answer explains a way to do this:

  1.) If you’ve already installed OpenJDK . Remove it by running this command:
  sudo apt-get purge openjdk*

  2.) Then:

sudo add-apt-repository ppa:webupd8team/java

  Then update:

sudo apt-get update

  3.) Select which version you want
  To install Oracle Java 8:

sudo apt-get install oracle-java8-installer

I guess Oracle JDK 8 will work, but you can also install the older JDK 6 to be on the safe side.


File system     Dim. Usati Dispon. Uso% Montato su
udev            4,2G     0    4,2G   0% /dev
tmpfs           831M  2,1M    829M   1% /run
/dev/sdb1       487G  7,8G    455G   2% /
tmpfs           4,2G   79M    4,1G   2% /dev/shm
tmpfs           5,3M  4,1k    5,3M   1% /run/lock
tmpfs           4,2G     0    4,2G   0% /sys/fs/cgroup
/dev/loop1      4,4M  4,4M       0 100% /snap/gnome-calculator/406
/dev/loop0      4,0M  4,0M       0 100% /snap/gnome-system-monitor/107
/dev/loop2       47M   47M       0 100% /snap/gtk-common-themes/1353
/dev/loop3       16M   16M       0 100% /snap/gnome-characters/254
/dev/loop4      4,5M  4,5M       0 100% /snap/gnome-calculator/544
/dev/loop5      1,1M  1,1M       0 100% /snap/gnome-logs/81
/dev/loop6      4,0M  4,0M       0 100% /snap/gnome-system-monitor/77
/dev/loop7       16M   16M       0 100% /snap/gnome-characters/359
/dev/loop8       94M   94M       0 100% /snap/core/6673
/dev/loop9       58M   58M       0 100% /snap/core18/1223
/dev/loop10      38M   38M       0 100% /snap/gtk-common-themes/1198
/dev/loop11      57M   57M       0 100% /snap/core18/941
/dev/loop12     159M  159M       0 100% /snap/gnome-3-28-1804/31
/dev/loop15     1,1M  1,1M       0 100% /snap/gnome-logs/61
/dev/loop13      94M   94M       0 100% /snap/core/7917
/dev/loop14     164M  164M       0 100% /snap/gnome-3-28-1804/91
tmpfs           831M   13k    831M   1% /run/user/123
tmpfs           831M   33k    831M   1% /run/user/1000
/dev/sdc1       1,1T  632G    369G  64% /media/andrea/HDD EXT AND


What directories should I backup before a clean install of Ubuntu 20.04?

I would recommend you to copy/backup your /home directory.
List down the names of packages installed on your system
dpkg --get-selections > package_list.txt

You can read about How to list all installed packages.
Note: Before restoring the backup you should always take care of files (~/.bashrc and other files starting with . as prefix. In my opinion I would never copy files starting with . as some of might be system dependent) user directories.


Selling PC with Lubuntu, need clarification on legality

You are allowed to sell it at the same price you would sell it if you had installed absolutely nothing on it.  This means that the price should concern the PC only.  You are not allowed to sell or get any money for the software you have installed on it.  It's all free.


I have looked around, even in the source of Unity, and it does not seem like there is a way to do this.

Obviously, the Ubuntu developers don't share the opinions in http://www.jwz.org/xscreensaver/toolkits.html, but they should respect that others might do, and not prevent users from choosing their own screensaver. Several bugs has been found already in the new lockscreen.


Difference between package and source on http://packages.ubuntu.com/

Visit ubuntuupdates:

  Package "gcc-defaults"

  This package is just an umbrella for a group of other packages, it has no description.
  Description samples from packages in group:

GNU C preprocessor (cpp)
Documentation for the GNU C preprocessor (cpp)
GNU C++ compiler
GNU C++ compiler (multilib files)

  Packages in group

  cpp cpp-doc g++ g++-multilib gcc
  gcc-doc gcc-multilib gccgo-doc gcj-jdk gcj-jre
  gcj-jre-headless gfortran gfortran-doc gfortran-multilib gobjc
  libgcj-bc libgcj-common libphobos-dev

Hence gcc-defaults is head/source/umbrella package for gcc, gfortran etc.


Forgot default keyring password Ubuntu 14.10

Here's how to delete your current gnome keyring:

 rm ~/.local/share/keyrings/login.keyring

That should work, but I'm not entirely sure what all will be effected though. You could try & save the old keyring with instructions from here though I'm not following step 2 "create a new keyring", might mean to use seahorse - other users suggest that seahorse alone can fix the problem too.


OMEN by HP Laptop 15-dh0xxx, Realtek ALC285, Ubuntu 20.04 LTS - Microphone doesn't work

This is a known bug :Microphone not working in Ubuntu 18.04.3 LTS
What worked for me was the steps indicated in the post #63:
Execute arecord -l.
You will get something similar to this :
**** List of CAPTURE Hardware Devices ****
card 0: PCH [HDA Intel PCH], device 0: ALC3254 Analog [ALC3254 Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

Take note of the Subdevices 1/1 line.
Now edit /etc/modprobe.d/alsa-base.conf as sudo. Remove the lines you added and put these 2 instead:
options snd-hda-intel dmic_detect=0
options snd-hda-intel index=XXXX model=laptop-dmic

where XXXX is either :

0 if you had Subdevices : 0/1
1 if you had Subdevices : 1/1

Then save and reboot.
The bug behaves differently for different hardware so you may or may not need options snd-hda-intel dmic_detect=0. For some people it disabled sound but it is the opposite for me, sound does not work if I comment this line out.
If it still does not work I recommend reading the whole launchpad discussion because the different fixes had varying success depending on hardware and OS version.
I hope I helped.


I had made a backup of my home directory files.

I have reinstalled Xchat and removed the files from my home directory ~/.xchat2.

After reinstallation I verified Xchat working again and restored some configuration files from my backup.

Case closed.


try using a public DNS , because not accessing a site is due to not finding its ip address or not finding the server, so not accessing SOME sites means you can access others , so you internet access is good except that you are not resolving some names,
try using 8.8.8.8 , 8.8.4.4


Wired Network Does not Connect on first Boot

I don't know if this will be of any help. Just a thought...

Do you switch on your Internet connection just before switching on your computer? Sometimes, it can take a cable/broadband modem/router as much as two-three minutes to start completely. If this is the case, then switch on your Internet connection and wait for some time before starting your computer.


http://www.everydaylinuxuser.com/2013/09/install-ubuntu-linux-alongside-windows.html

What is happening here is that UEFI and secureboot are new features for booting with windows 8, and Linux isn't smart enough to handle it yet.  This guide tells you step by step how to do the manual pieces for now.


I have encountered the same problem with you and now I have solved it. Maybe my solution helps you. You have mentioned that this issue happened after a repair of Grub, so open the apt log file (var/log/apt/history.log) and check the last time when it worked, then you can revert(remove or reinstall) the package that you changed the last time. Then reboot, hope it works for you.


Install dconf-editor.

sudo apt-get install dconf-editor

Start and goto: com > canonical > unity > panel and edit: systray-witelist ['all']


When prompted what does Administrative Password refer to?

Whoever installed the Ubuntu system was asked for a user name. That user name not only became the first user of the system, but also became the first sudo user (account that could put sudo to run root-privileged programs.

So, your password should work. If you did not install the system, you need to go on the sudoers list. These two questions should help you add your account to sudoers, but you still need the first account's password, if it was not you.

To check to see if you have admin privileges, try entering sudo -i and using your regular password. If that works, it would help to have more information about what you are trying to run.


Visual glitches when rotating display - ATI Radeon

I am using Lubuntu 16.04 as well but this problem you are experiencing is related to the combination of using Ubuntu 16.04 (or higher) with ATI Radeon video cards (GPUs). Why?

Ubuntu uses totally different ATI Radeon drivers between version 14.04 and 16.04. Ubuntu 14.04 used AMD Radeon's proprietary drivers (called "fglrx"). Ubuntu 16.04 uses AMD Radeon OpenCL drivers (called "AMDGPU-PRO").

As a result of this huge switch over (done by AMD) to move away from their proprietary drives and instead use OpenCL drivers (which in the long-run is great of course and NVIDIA hasn't made the jump to OpenCL yet) they (AMD) are behind on coding full featured drivers for their products in OpenCL. Thus you can't rotate a display yet and other buggy problems. I don't think of rotating a display as an edge case but here is a guy complaining he can't get more than 8 GPUs to work!

I bought an AMD Radeon RX 480 video card that only has the new AMDGPU-PRO drivers for it!


If I fill my harddrive, why can't I log in?

If the root partition has filled (or the partition that holds /var to be more precise), there will not be any space to write to /var/log/auth.log, which usually prevents login attempts from anyone besides the superuser.

The same goes for /home. There are files in your home directory that have to be updated and if there is no space left on the device will prevent you from logging in.


How can I make the nfs server support protocol version 2 in Ubuntu 17.10?

You need to modify /etc/default/nfs-kernel-server to have these lines:

RPCNFSDOPTS="--nfs-version 2,3,4 --debug --syslog"
# To confirm above mods are in effect after service restart use
#     cat /run/sysconfig/nfs-utils
#  or
#    service nfs-kernel-server status
#

and restart the service

service nfs-kernel-server restart

take care that after service restart you may need to re-start shares

zfs share -a

Finally confirm that protocol 2 is being supported (tcp and udp too if necessary)

rpcinfo -p servername | fgrep nfs

You should see this

100003    2   tcp   2049  nfs
100003    3   tcp   2049  nfs
100003    4   tcp   2049  nfs
100003    2   udp   2049  nfs
100003    3   udp   2049  nfs


KASLR disabled: could not find suitable E820 region!

Boot Fix

In order to boot properly in the first place, highlight your Ubuntu option and press e to edit the boot parameters. Manually insert nokaslr behind quiet splash and then press F10 to continue booting.

Permanent Fix

Using sudo powers edit your /etc/default/grub and add the option nokaslr to the line:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nokaslr"

You may have other options besides quiet splash which you will want to leave in place. Save the file and exit your editor. Then run:

sudo update-grub

Second Option

If inserting nokaslr above doesn't work, then repeat both sections above but insert kaslr instead.

TL;DR

KASLR randomizes the layout of Kernel address space making it harder for snooping programs to hack kernel working storage and obtain passwords. It was superceded by KAISER which was superceded KPTI (Kernel Page Table Isolation) for Meltdown and Spectre Security hole violations.


I've a problem while configuring Ubuntu 18.04 to switch between Arabic and English using Alt-R + Shift-R

The Arabic layout makes Right Alt the 3rd level modifier key automatically. However, the lv3:ralt_alt XKB option makes Right Alt to work as any Alt, so possibly this command will make a difference for you:

gsettings set org.gnome.desktop.input-sources xkb-options "['lv3:ralt_alt']"


Although the Macauley2 Repository may not be working the Bionic Beaver Debian files work well enough when downloaded and installed directly. Install as follows:

sudo apt-get install libblas3 libgfortran4 liblapack3 libquadmath0
wget https://faculty.math.illinois.edu/Macaulay2/Repositories/Ubuntu/dists/bionic/main/binary-amd64/Macaulay2-1.14-amd64-Linux-Ubuntu-18.04.deb
wget https://faculty.math.illinois.edu/Macaulay2/Repositories/Ubuntu/dists/bionic/main/binary-amd64/Macaulay2-1.14-common.deb
sudo dpkg -i *.deb

This installed cleanly on my own Bionic system and appears to be functional:

andrew@corinth:~$ M2
Macaulay2, version 1.14
--storing configuration for package FourTiTwo in /home/andrew/.Macaulay2/init-FourTiTwo.m2
--storing configuration for package Topcom in /home/andrew/.Macaulay2/init-Topcom.m2
with packages: ConwayPolynomials, Elimination, IntegralClosure, InverseSystems, LLLBases, PrimaryDecomposition,
               ReesAlgebra, TangentCone, Truncations

i1 :

And hopefully all will be well on your system as well :)


How to stop XDM performing automatic downloads

Try the latest version.
This problem is fixed in version 4.7 for Linux
There is a checkbox added in the new download dialog, which can add the unwanted link to download ignore list.


I just had this same problem, my solution was: (if you are a newbie memorize it and then do it).

Go to a tty by pressing Ctrl+Alt+F1
Press your Touchpad's  enable-disable key: (in my case) Fn+F7
Switch back to X by pressing Ctrl+Alt+F7

(If your Touchpad wasn't re-enabled, press again your Touchpad enable-disable key: Fn+F7)
Before I found this I had tried everything out there but couldn't get it to work until I noticed the button (Fn+F7) used by Ubuntu to enable-disable the Touchpad was the same my laptop's hardware uses, so the issue wasn't that Linux didn't enable the Touchpad, it was that I had two systems (Linux and hardware) enabling and disabling my Touchpad for some reason, they were out of phase, when one enabled, the other disabled. (You can actually make this happen by running my solution again).


Finding which program has created a specific file

In general, if you run a program which creates a file, the file will be owned by your user. There is no way to know what program created it. For example, if I create two identical files with different programs:
$ bash -c "echo hello > file1"
$ sh -c "echo hello > file2"

There is nothing in the file attributes that distinguishes the files:
$ ls -l file1 file2
-rw-rw-r-- 1 user group 6 Dec 21 11:47 file1
-rw-rw-r-- 1 user group 6 Dec 21 11:47 file2

But you might find some clues:

In the pathname, e.g. ~/.thunderbird/ or ~/.zshrc

In the file itself, e.g. ~/.zcompdump contains shell arrays, and the z in the filename makes me think Zsh created it.
The file utility might be useful for identifying filetype. (I can't think of a good example, but the usage is like file ~/.zcompdump, which prints /home/user/.zcompdump: ASCII text)


Go into the directory which contains mysql-proxy-0.8.2-platform.tar.gz from terminal.
After that run the below command to extract the mysql-proxy-0.8.2-platform.tar.gz file inside the /usr/local.

tar zxf mysql-proxy-0.8.2-platform.tar.gz -C /usr/local

To set the environment path

su root
PATH=$PATH:/usr/local/mysql-proxy-0.8.2-platform/sbin


My Linux install bricked itself (ACPI, Couldn't get size: 0x800000000000000e and PKCS#7)

answering my own question here for visibility, the ACPI errors and PKCS in the log actually have nothing to with the real problem i had. gonna quote my own comment from the other answer.
"Alright, so I found the issue. Yesterday I formatted one of my drives to ext4 from ntfs because the specific application required me to use ext4 partition. However, I didn't made necessary changes to /etc/fstab to let the system know it's no longer NTFS. To fix this, I had to remove extra drive mount points from that file, save, reboot."
basically, it just got stuck on this step of the boot process because it was unable to mount the drive.


Formatting C:/ in Windows while ubuntu is installed in D:/

You have to re-install WUBI to use Ubuntu after the re-installation of Windows.Do the following

Re-install Windows
move your root.disk file in the D:\ubuntu\disks folder to any place you like (except in the Ubuntu folder, because reinstalling wubi will delete the ubuntu folder)
Install Ubuntu using Wubi to D:\ partition
After installation is finished, replace the Root.disk file with the old Root.disk file (that we backed up in the step 2)
Restart.


How to check if a variable is empty on command line?

You could use while [ "$USER_NAME" == "" ] ... or while [ -z $USER_NAME ].


How can I identify my Wifi network device?

Running dmesg | grep -i sdio (finally) produces:

[    3.396231] mmc1: new high speed SDIO card at address 0001
[   37.677841] brcmfmac: brcmf_fw_map_chip_to_name: using brcm/brcmfmac43430a0-sdio.bin for chip 0x00a9a6(43430) rev 0x000000
[   37.686764] brcmfmac mmc1:0001:1: Direct firmware load for brcm/brcmfmac43430a0-sdio.txt failed with error -2
[   38.704097] brcmfmac: brcmf_sdio_htclk: HT Avail timeout (1000000): clkctl 0x50
[   39.712130] brcmfmac: brcmf_sdio_htclk: HT Avail timeout (1000000): clkctl 0x50

So I guess the mistery is solved! The sound card appears to be a Broadcom BCM43430. I'm trying something from https://patchwork.kernel.org/patch/9791523/ to solve the issue, haven't succeeded yet, but I don't want to go OT.

Maybe it would be useful to add the dmesg | grep -i sdio command to  https://help.ubuntu.com/stable/ubuntu-help/net-wireless-troubleshooting-hardware-check.html.en but I didn't see a link to suggest an update.

Thanks everyone!


This is the default wallpaper of ubuntu 14.10.You can find it here.


How can I logout from the GUI using CLI?

To end all user processes and be sent back to the login screen, you can use:

kill -9 -1

Don't run it as root though, for reasons discussed here.


Did you try enabling "Tear Free desktop" in the Catalyst control center. This fixed the issue for me across all distros.

But given that you are left only with "legacy" catalyst driver, it seems to be a good solution to use the ever improving AMD OSS drivers. Make sure you use the latest 3.7 / 3.8 kernel to get all the benefits that has been going into the OSS driver stack.


White screen on one monitor after logon... how to fix?

Turns out that my problem was related to my understanding of setting up multiple monitors.

I took it that TwinView meant that it would 'mirror' the display so was trying to use seperate X windows.

Eventually worked this one out!


Bumblebee setup on Dell XPS 15 9530 for dual monitors in Ubuntu 13.10

I spent a day doing this specifically on the XPS 15 9530. I finally got it working after looking at many different (and conflicting) sources. I started a write-up on it, which outlines how to get it to work. It is still a work-in-progress, but I hope the guide will get it working for you. As of right now, this guide covers it up to the point of getting Bumblebee to work. I have not done the multi-monitor setup yet, but I figure this will get you closer.

http://wiki.belmankraul.com/linux/mint16_bumblebee


Battery indicator is stuck on "estimating"?

This is known bug that affects HP, Compaq, Dell and other manufactures. This is because of a change made in gnome-power-manager where by the estimate is done on time remaining, rather than percentage. This change does not play nice with some hardware and is why you are seeing (estimaing...) constantly.

The bug report about it is here if you fancy a read:
https://bugs.launchpad.net/ubuntu/maverick/+source/gnome-power-manager/+bug/629258

At this time, I believe there is no fix available. However you can click on the estimating... and it will bring up a more detailed view of your battery info, which will display the percentage of charge.


My install did not install the grub loader and I also can not get to windows 7 either

Boot from a Ubuntu live CD/DVD/USB or whatever, open a command line, and run the command sudo grub-install /dev/sda (if you don't want GRUB on your primary hard drive, change sda to whichever hard drive you want it installed on).


How can I convert from uppercase to lowercase all directories and sub-directories in Ubuntu 16.04.2?

find /path -depth -exec rename 'y/[A-Z]/[a-z]/' {} ";"

Here is a simple directory structure:

$ mkdir -p A/B/C/D
$ tree
.
└── A
    └── B
        └── C

and after running rename using find:

$ find /path -depth -exec rename 'y/[A-Z]/[a-z]/' {} ";"
$ tree
.
└── a
    └── b
        └── c


A number of Linux drivers seem to be sensitive to the access point to which they attach. First, check the settings in the router. WPA2-AES is preferred; not any WPA and WPA2 mixed mode and certainly not TKIP. Second, if your router is capable of N speeds, you may have better connectivity with a channel width of 20 MHz in the 2.4 GHz band instead of automatic 20/40 MHz, although it is likely to affect N speeds. I also have better luck with a fixed channel, either 1, 6 or 11, rather than automatic channel selection. Also, be certain the router is not set to use N speeds only; auto B, G and N is preferred. After making these changes, reboot the router.

Next, I'd set IPv6 to Ignore in Network Manager: http://docs.fedoraproject.org/en-US/Fedora/18/html/Installation_Guide/images/netconfig/network-connections-ipv6-ignore.png  This example is for ethernet, but you want wireless.

If these changes do not help, please try:

sudo modprobe -r rt2800pci
sudo modprobe rt2800pci nohwcrypt=Y

If it helps, make it permanent:

sudo -i
echo "options rt2800pci nohwcrypt=Y"  >  /etc/modprobe.d/rt2800pci.conf
exit

Finally, Network Manager will default to ethernet if it's available. Please make your tests with the ethernet detached.


further down on their page it says

  You can prevent the installer from asking for the installation
  directory by specifying it in the install command itself, as shown
  below:

sudo python -c "import sys; py3 = sys.version_info[0] > 2; u = __import__('urllib.request' if py3 else 'urllib', fromlist=1); exec(u.urlopen('http://status.calibre-ebook.com/linux_installer').read()); main(install_dir='/opt')"

  Change /opt above to whatever directory you want calibre automatically
  installed to.

Presumably that means its default is /opt/calibre

On my system its in /usr/lib/calibre but it was installed through the ubuntu repo (NOT ADVISABLE but my school admin doesn't want unofficial installs of anything). So I can't confirm it but I'd be surprised if it isn't there.

Try seeing if the modified command works. If that doesn't work, search your filesystem for the calibre directory, then just replace /opt in main(install_dir='/opt')  to the directory calibre is installed in.


No Apt found after installing 64-bit Ubuntu core 18.04 on Raspberry Pi 3B+

Ubuntu core 18.04 only has Snap for package management.


I finally got this to work by including the -f option:

-f, --full
    The pattern is normally only matched against the process name.  When -f is
    set, the full command line is used.

With which:

$ pgrep -f myprocess
1234


How do I install the latest Blender 3D builds from a PPA?

IF you Actually click on the links you can find out why, the address just doesn't exist.

And if you  go to the launchpad page: https://launchpad.net/~cheleb/+archive/blender-svn you can see it's not accessible.

@PhoneixS asked the maintainer of the PPA Ralf Hölzemer (cheleb) and he said:  "...cannot maintain that PPA any longer."

You can however Install it from this other PPA:

https://launchpad.net/~thomas-schiex/+archive/ubuntu/blender

sudo add-apt-repository ppa:thomas-schiex/blender
sudo apt-get update
sudo apt-get install blender

The builds are recent so you still get the newest Blender.

Here you can find Instructions on how to Compile Blender from SVN

http://wiki.blender.org/index.php/Dev:2.5/Doc/Building_Blender/Linux/Ubuntu/CMake


Android M phones don't display all content in Thunar via MTP

According to go-mtpfs

Go-mtpfs is a simple FUSE filesystem for mounting Android devices as a MTP device.
It will expose all storage areas of a device in the mount, and only reads file metadata as needed, making it mount quickly. It uses Android extensions to read/write partial data, so manipulating large files requires no extra space in /tmp.
It has been tested on various flagship devices (Galaxy Nexus, Xoom, Nexus 7). As of Jan. 2013, it uses a pure Go implementation of MTP, which is based on libusb.

install the Go compiler suite; e.g. on Ubuntu:
sudo apt-get install golang-go
Install libmtp header files
sudo apt-get install libusb1-devel

Then run
mkdir /tmp/go
export GOPATH=/tmp/go
go get github.com/hanwen/go-mtpfs

/tmp/go/bin/go-mtpfs will then contain the program binary.
You may need some tweaking to get libusb to compile. See the comment near the top of usb/usb.go, ie.
 # edit to suit libusb installation:
 vi /tmp/go/src/github.com/hanwen/go-mtpfs/usb/usb.go
 go install github.com/hanwen/go-mtpfs

A 32 and 64-bit linux x86 binaries are at
go-mtpfs
USAGE
mkdir /tmp/go
GOPATH=/tmp/go go get github.com/hanwen/go-mtpfs
sudo mv /tmp/go/bin/go-mtpfs /usr/bin/
mkdir ~/Android

to mount device:
go-mtpfs ~/Android


How do I DISABLE home directory encryption during Ubuntu 12.04 installation?

I ran in to this as well, specifically after a prior install where I had chosen for an encrypted home directory.

Deleting all existing volumes and partitions on the disk through a separate tool seemed to fix the problem, and now the options are all selectable again.


Lenovo ThinkPad P52 + Ubuntu Studio; Doesn rogognize secon monitor

I recommend using Section 5 of this Guide by Lenovo. It helped me getting external monitors to work on my P53.

In short. Installing the proprietary NVIDIA drivers should fix your external monitor. The guide suggests sudo apt install nvidia-driver-430, however there are newer versions of the driver (435 and 440) available. I am using 440 and it works.

Regards


Firefox: Long lines in text area not visible

I can see 2 methods that will partially meet your needs:

The masking or wrapping of such lines in Firefox are because Firefox by default obeys the css built into the page. One way to view the page without the css, and thus see the raw number display, is to install the web developer toolbar:

Web Developer

and then toggle the css display by using the key combination:

Alt+Shift+A
Another choice is to perhaps permanently display all long lines without line wrapping. This was a behavior introduced with Firefox 22 as explained here. To reverse this you will need to follow these steps (taken from the linked article):

Type about:config into the address bar and hit enter.
Confirm that you will be careful if this is the first time you open this page
Use the search at the top to filter for plain_text.wrap_long_lines.
Double-click the value to set it to false which deactivates the feature.
To restore the original value at any time, repeat the steps abov

Not exactly what you are after but probably as close as you will get...


The URL you are using is wrong, you are trying to add the repository file as a URL!
Just use this as URL:

https://xpra.org/ disco main


How can I toggle selected pulseeffects equalizer profile from command line?

if I understood your question correctly..

for example, if you have 3 profiles like V1, V2 & V3 and you would like to select profile V1, you can run the below command

gsettings set com.github.wwmm.pulseeffects last-used-preset 'V1'

if you dont want this, you can use below command

gsettings reset com.github.wwmm.pulseeffects last-used-preset

you can create a script with below content and call it with a shortcut you wish.

#!/bin/bash

key="com.github.wwmm.pulseeffects last-used-preset"
current=$(gsettings get $key)

if [ "$current" == "'V1'" ]; then
  gsettings reset $key
else
  gsettings set $key "V1"
fi

Courtesy by @MichalPrzbylowicz for toggling on and off

dconf write /com/github/wwmm/pulseeffects/sinkinputs/equalizer/state true
dconf write /com/github/wwmm/pulseeffects/sinkinputs/equalizer/state false


Remove spaces in a = "test"; to be a="test";


Ubuntu 18.04.2 LTS Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine"

I ran a complete uninstall of VMware. Did a reload of the box. Ran the install again and it took. Not sure what was up originally but now the issue has cleared.


How can I connect ubuntu 19.10 to a projector?

OK I got it to work by connecting HDMI-to-VGA converter to the projector and all options in the Display Settings appeared successfully.


Installing a 10.10 package on a 10.04 LTS

You may try using ppa:maco.m/ruby PPA

Another option is to build it from source (using instruction from here):

sudo su
apt-get install build-essential
apt-get install ruby rdoc libopenssl-ruby
wget http://production.cf.rubygems.org/rubygems/rubygems-1.3.7.tgz
tar zxvf rubygems-1.3.7.tgz
cd rubygems-1.3.7
ruby setup.rb
ln -s /usr/bin/gem1.8 /usr/local/bin/gem


There is no way to change device names in /dev directory. Maybe this is not statued for input devices like gamepads. I cant test this because I have no gamepads around.

But this will be necessary for your approach. So, the first answer is: It is impossible.

The second answer is more a hint to a way which may help you to deal with your idea:

As you may assign symbol links to devices using udev rules, maybe you can deal with it that way. I will explain it by means of a usb-stick.

What we do is:

- Disconnect the usb stick using a command
- create a temporary rule for assigning a symlink
- Reconnect the usb stick using a command
- delete the temporary rule

For the background read these articles: udev, about udev rules, Authorizing USB devices and sudo echo access denied

As a prerequisite we need some information about the targeting usb stick.
Remove the stick and run the command

udevadm monitor

Plug the stick in an you get a lot of information on the screen. I extract the device path on the usb bus from the first line of output:

add      /devices/pci0000:00/0000:00:1d.0/usb4/4-1/4-1.1 (usb)
                                                   ^^^^^

With this information run the command

udevadm test /sys/bus/usb/devices/4-1.1
                                  ^^^^^

Again there is a lot of output. We are interested in

ID_SERIAL_SHORT=08606E5EDA173E6D3F37746D

This is an unique serialnumber to the usb-device.

Now lets give this stick an symlink.

First we have to disconnect our usb stick:

echo 0 | sudo tee /sys/bus/usb/devices/4-1.1/authorized > /dev/null

Now we create a temporary rule for udev:

echo "KERNEL==\"sd?1\", SUBSYSTEMS==\"usb\", ATTRS{serial}==\"08606E5EDA173E6D3F37746D\", SYMLINK+=\"myusb300\"" | sudo tee /etc/udev/rules.d/90-tmp-001.rules > /dev/null

Next step is to reconnect the usb stick:

echo 1 | sudo tee /sys/bus/usb/devices/4-1.1/authorized > /dev/null

Now you find a symlink /dev/myusb300 to /deb/sdb1

The idea behind all this is, even if you can't rename /dev/js0, you can create symlinks, i.e. /dev/js10, to the gamepad controller. This symlinks can be swapped, just on thy fly or by programmatic disconnect and reconnect the controller. The application (the game) itself should be configured to use the gamepads /dev/js10, /dev/js11, and so on.

By the unique serialnumbers of the gamepads you may always assign a specific symlink to a choosen gamepad.

Maybe it is possible to find more possibilities dealing with udev. That depends not only on the concrete solution you are looking for but also on the application, the controllers and other things.


Windows arranged strangely on multiple desktop after detaching external monitor

This has been confirmed as a bug in Compiz and filed here:
https://bugs.launchpad.net/compiz/+bug/763148

I agree it is very tedious. If you have any extra info to add, or to mark the bug as affecting you, use the link above.


When cd is inserted it will not play 16.04

First off ensure that auto-play settings are turned on. Go to System Settings, Details, Removable Media and this screen appears:

If your screen looks like this then uncheck the last box and change the default for audio CD's to RythmBox to ensure CD's auto-play.


What is the "Waiting Channel" of a process?

The waiting channel is the place in the Kernel where the task
is currently waiting. A task has to wait for a Resource, which
can be data or processing time. These two include network sockets, hardware, files, and so on; since most of them are just files, in Unix-like systems.

0: The process isn't waiting
poll_schedule_timeout

poll() is a system call1 used to handle I/O.
It's similar to select().2

Applications that use non-blocking I/O use these calls to see if they
can read from or write to a file, withouth having to block it. They are
often used for input/output streams, which may not be blocked (otherwise,
perhaps your mouse would stop to move).

The waiting channel poll_schedule_timeout indicates that a task is
waiting for I/O, either hardware like keyboards and mice, sound devices
or even network sockets.

A function in the Kernel
They are defined in <linux/poll.h>. poll was an implementation first
seen in System V, select is the BSD UNIX equivalent.

futex_wait_queue_me:

To explain this, we have to look at Locks. A lock is a saved state in the
system that indicates that a task works with a resource. There can be, for
example, only one task that reads a file. This task would lock the file, any
other task1 that tries to read the file would know it's locked, and wait for
the lock to go away, before it can access it. The same thing happens for
processor time.

Modern version of Linux (on most architectures) use a Futex (fast userspace
mutex) lock in the kernel. Mutex, mutual exclusion, refers to the idea that
a common resource can only be accessed by one task at any time. For this, flags
in the system are set.

If a process is waiting for a locked resource, this is called Busy Waiting
or "Spinning", refering to the fact that it tries to access it over and over,
until it can. A task is said to be blocked when it spins.

Futex locks can be thought of as a number in userspace, that can be incremented
or decremented by a task (in cases where the resource can be accessed by
multiple tasks, this number can become greater than one). This is the number
shown in the diagram4.

These tasks enqueue themselves in the wait queue, a simple queue of tasks that need to do some work,
once processing time is available, the tasks do their work and are removed
from the queue.

futex_wait_queue_me enqueues a tasks. It then waits for a signal, a time
out or a wakeup. Task that are in this waiting channel are waiting not
on the wait queue, they are waiting to be enqueued.

A task can be either a Process3 or a Thread2
A Thread is a sub-section of a Process. Many threads can run parallel
A process is a full-blown program, it consists of one or more threads, though a program can consist of multiple processes as well.
Remember, this is still a very high level view of things, it's not considering the implementation details

__skb_recv_datagram

Wait for some data on a locked network socket.
sk_wait_data

Wait for some data on a network socket.
do_exit

This is the last part of quitting a process. do_exit() calls the schedule() next, to schedule another process. When do_exit() is called, the process is a ZOMBIE.
do_wait

A process is added to the schedulers wait queue.
pipe_wait, unix_stream_data_wait

A Process is waiting for data from a subprocess. This happens, for example, when you run this sort of code:

echo | sleep 10 && echo hallo              # pipe

or

cat < hello.c                              # unix data stream

hrtimer_nanosleep

The process is sleeping, using the hrtimer_nanosleep() method. This method can be used for a program to sleep for specific intervals of time, with nanosecond accuracy.

These aren't all, but I didn't observe any others. Post a comment if I've missed anything.


Intel GMA 950 missing driver for an EEE PC 1008HA

This is a similar situation to what I had with my Intel® 965GM. My system info was also showing my graphics card as unknown in Ubuntu 11.10, and after a while (a few days later I installed Ubuntu 11.10) my Unity 3D was broken. I could be able to select "Ubuntu" but it acted like I was using Unity 2D.

I found out that it is related to OpenGL and I applied this command:

1.Remove NVidia drivers

(I know you didn't install any NVidia drivers, I also didn't install but in my case there were NVidia drivers installed somehow.)

sudo apt-get purge nvidia*

2.Remove your xorg.conf

sudo rm /etc/X11/xorg.conf

3.Reinstall xorg completely

sudo apt-get install --reinstall xserver-xorg-core libgl1-mesa-glx:i386 libgl1-mesa-dri:i386 libgl1-mesa-glx:amd64 libgl1-mesa-dri:amd64

4.Re-configure Xorg

sudo dpkg-reconfigure xserver-xorg

5.Restart your computer

sudo reboot

After I applied all of these commands, my Unity 3D was back and when I check system info, this time Ubuntu recognized my Intel graphics.


Wifi won't connect on Ubuntu 17.04 with Windows 8.1 dual boot

There are probably two things wrong. First, open a terminal by pressing Ctrl + Alt + T and run:

gksudo gedit /etc/NetworkManager/NetworkManager.conf

Use nano or kate or leafpad if you don't have the text editor gedit. At the bottom of this file, copy and paste the following:

[device]
wifi.scan-rand-mac-address=no

The final result will look like this

[main]
plugins=ifupdown,keyfile

[ifupdown]
managed=false

[device]
wifi.scan-rand-mac-address=no

Proofread carefully, save and close the text editor and then run:

sudo service network-manager restart

Next, it is likely that you have two possibly conflicting drivers loaded. Check:

lsmod | grep rtl

I suspect that two drivers are listed, rtl8xxxu and also rtl8192cu. If so, you need just one. Again, from the terminal:

sudo -i
echo "blacklist rtl8192cu"  >>  /etc/modprobe.d/blacklist.conf
modprobe -r rtl8192cu
exit

Any improvement? It might take a reboot.


Remove all borders and tab bars from Yakuake?

-this is one workaround to the large tabbar at bottom of yakuake window"

One Pixel Title: A clean interface but for the one pixel line at the bottom of the window.


Argus Camera DC-1512E will not transfer photos

Shotwell's digital camera support comes from GPhoto.  A list of supported cameras is here:

http://www.gphoto.org/proj/libgphoto2/support.php

Since your camera isn't on the list, it may not be supported; though since there's a couple similar model numbers mentioned I'd still think it ought to work.

You might try asking on the GPhoto mailing list if there's any known issues with that camera.


Dual boot with encrypted Windows partition

Try installing Windows Bootloader on another partition then chainload from GRUB then from there boot into Windows.


I finally stopped procrastinating and tried it, only to discover that 1003 did not appear anywhere in /etc/passwd or /etc/groups; somehow that user and group were lost during the disk transfer.
I solved the problem in what I think is a relatively safe way by changing only those files owned by 1003:1003 to a new owner:
This worked in Ubuntu 18.04:
chown -R --from=<old_owner>:<old_group> <new_owner>:<new_group> <directory>

...but I think some Linux distributions don't allow the --from flag, so this should work in those cases:
find . -user <old_user> -group <old_group> -exec chown <new_user>:<new_group> {} \;

Thanks to @Stephen Boston for advice.


How can you test for a DNS leak for an OpenVPN provider?

OpenVPN won't assign server's DNS resolver(s) if you run it from
  terminal. This is a known behavior and until OpenVPN developers fix
  it, you have to run an external script to assign the DNS resolvers
  once the tunnel is connected, and revert when disconnected. This
  should work on Ubuntu, Debian, and any Debian based distros.

  Step 1

  First, you have to update the .ovpn profiles to run a script that
  will assign a DNS resolver and restore your original resolver when
  the VPN connection will shut-down. Add the following lines to the
  .ovpn file:

script-security 2
up updatedns.sh
down updatedns.sh

  Note that this applies if you run openvpn [server profile.ovpn] from
  the current folder, not eg.

openvpn /home/myself/Downloads/openvpn-profiles/server-location.ovpn

  If you run from different folder, you will have to include the full
  path accordingly (also to the mass-update command below)

  To mass-update all .ovpn profiles in a folder, unzip the server
  profiles, then from the same folder run:

for filename in *.ovpn; do  echo -e "script-security 2\nup updatedns.sh\ndown updatedns.sh" >> $filename; done

  Step 2

  Get the updatedns.sh script:

wget https://vpn.ac/configs/misc/updatedns.sh

  Run chmod +x updatedns.sh to make it executable Step 3

  Connect by running:

openvpn ./[location-profile].ovpn

  Once connected, check dnsleak test. It should report our DNS
  resolvers.

  When you disconnect, the original resolv.conf will be restored.
  If anything goes wrong it it doesn't restore properly (ie. openvpn
  process killed), restore it manually by running:

cp -a /etc/resolv.conf.orig /etc/resolv.conf

Source:VPN.AC


Accessing via Nautilus by typing 'dav://url.com/Folder' is as fast as can be, but mounting it is extremely slow.

Please create an Ubuntu One account and at the top of the bug below click on "This bug affects xx persons. Does this bug affect you?" and confirm "yes this bug affects me". This helps to give you a real answer/solution and not having to use dav://. On the right side you can also click "You are not directly subscribed to this bug's notifications.", and change if you want to be notified. This also adds to the "bug heat" (flame icon at the top).

https://bugs.launchpad.net/ubuntu/+source/davfs2/+bug/185986


How to install X11 Xevie extension to compile Xevie-based programs

I don't think that any package provides Xevie.h. There is a different library called xevie.h which is provided by libxcb-xevie0-dev but that's not what you need.

However, I did find this page which has what looks like the source packages. I tried downloading libXevie-1.0.3.tbz and I can confirm that it contains a file called Xevie.h that includes the functions from your comment. In fact, the file is so small I am reproducing the entire thing here:

/************************************************************

Copyright (c) 2003, Oracle and/or its affiliates. All rights reserved.

Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the "Software"),
to deal in the Software without restriction, including without limitation
the rights to use, copy, modify, merge, publish, distribute, sublicense,
and/or sell copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice (including the next
paragraph) shall be included in all copies or substantial portions of the
Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.

************************************************************/

#ifndef _XEVIE_H_
#define _XEVIE_H_

#include <X11/Xfuncproto.h>

#define XEVIE_UNMODIFIED    0
#define XEVIE_MODIFIED   1

#ifndef _XEVIE_SERVER_

_XFUNCPROTOBEGIN

Bool XevieQueryVersion(
    Display*            /* dpy */,
    int*            /* major_version */,
    int*            /* minor_version */
);

extern Status XevieStart(
    Display*            /* dpy */
);

Status XevieEnd(
    Display*            /* dpy */
);

Status XevieSendEvent(
    Display*                    /* dpy */,
    XEvent*         /* event */,
    int             /* data type */
);

Status XevieSelectInput(
    Display*                    /* dpy */,
    long
);

_XFUNCPROTOEND

#endif /* _XEVIE_SERVER_ */

#endif /* _XEVIE_H_ */

When looking for a specific file, you can search for it at http://packages.ubuntu.com or use apt-file:

$ apt-file search xevie.h
libxcb-xevie0-dev: /usr/include/xcb/xevie.h

As you can see, using apt-file search filename returns the package (if any) that provides the file. If apt-file is not installed, you will need to install it and generate its package list before running it:

sudo apt-get install apt-file
sudo apt-file update


Duplicate screen when starting Ubuntu 18.04 on laptop with AMD Graphics

I have had the same issue.
Try To select boot mode to UEFI in Bios and install ubuntu


Camera stopped working after OSB and KDELive installed

The problem was (as it is said in many answers) that the camera's lense was switched off.
Since it's a relatively new laptop that I got from my office I was unaware of this functionality.
It's a Lenovo thinkpad L490 that has a physical switch that shuts down the camera lense.
So here is the camera switched off

And here is how it looks when it is switched one and recording


Large amount of scrollable text in Ubuntu touch

You can use a TextArea to provide scrollable text and set the readOnly property to true.


Ubuntu Studio 20.04 FireWire compatibility

Using the ALSA backend, the ALSA firewire backend will continue to work so long as ALSA sees the device. The Firewire backend in Ubuntu Studio Controls was intended for devices that required FFADO, which proved to be problematic.

For that reason, since Firewire devices are ancient and no longer manufactured, unless they simply work with the ALSA backend, they will not be supported by Ubuntu Studio going forward.


Is there a way to check if others are logged into server when you are?

Just type who:
~$ who
(unknown) tty7         2013-12-06 13:37 (:0)
john      pts/0        2013-12-08 00:16 (192.168.0.100)
jane      pts/1        2013-12-08 00:17 (192.168.0.101)

EDIT
Regarding your bonus question :)
To see login history for users you can use last -i. This will show all logins and IP addresses since start of current logfile /var/log/wtmp.
Depending on your logrotate you can show previous logs with last -f /var/log/wtmp.1, too.
To only show the very last login for each user use last -i | sort -r | uniq -w 16
~$ last -i | sort -r | uniq -w 20
wtmp begins Sun Dec  1 16:54:49 2013
john    pts/0        192.168.0.100    Sun Dec  8 18:49   still logged in
jane    pts/1        192.168.0.101    Sun Dec  8 00:17 - 00:34  (00:16)


How do I disable the orange resizing of windows when I put them up against the edge of the screen?

The orange window is created by the "Grid" plugin. Deactivate it in CCSM if you don't want it.

To change the workspace activate the "Edge Flip" options in the "Edge Flipping" tab of the "Desktop Wall" plugin and activate the binding you want in the "Bindings" tab.


Cannot move window because the title bar is above the screen

Hold down "Alt", left click and hold in the window, and then move the mouse around. That should grab the window and let you move it.


System information disabled due to load higher than 4.0 but it ain't higher than 4.0

This can happen if the system is particularly busy at the moment you try to connect.
It's not Pi-specific, I've seen it on low-resource servers of several varieties.
One example where I see this more often: A slightly-too-early connection after a boot. The system is still working hard for a few more seconds to finish the boot jobs. A second connection a few seconds later, after the system has settled, is normal.
It's not just boot. If the system CPUs are simply busy running Minecraft Servers or ROS or hourly cronjobs or any other intensive task at the moment you coincidentally connect, you will get that message.


Why would I want to compile from binaries vs using sudo apt-get install

Using the official repos is making sure that the software you're installing is both tested and configured as it should be, in order to function as it should.  This does not mean that you cannot or shouldn't use several TESTED ppa's.  Most of them are quite ok to use and they are very safe.

apt-get installs software using the repos or ppa's as sources.  This also ensures that whenever new releases appear in those sources, your copy will also be updated during the update process.

Compiling from source should be your choice only in cases when the software you need does not exist as a precompiled package in the sources mentioned above or the precompiled versions are outdated and new ones do not exist.  Compiling from source makes you and only you responsible for that software and you should check for possible updates to that software manually.

You should also know that in order to be able to compile from source, many many more packages will have to be installed on your system, for the compiler to find them and create the compiled version.


Mounting a 2nd SDD skipped during installing 20.04.01

You can use the utility "Disks" if you prefer a graphical interface to configure a hard drive to be mounted automatically during startup. That can also be done by correctly adding the drive to the configuration file /etc/fstab. The latter method is explained in an earlier question.
A hard drive in linux is mounted on a folder in your file system. As such, the contents of the drive becomes available when visiting that folder, which is referred to as the "mount point". When using "Disks", the utility will suggest a mount point under /mnt/.


Cisco packet tracer isn't displayed in Activities

You can create a custom .desktop launcher for Cisco Packet Tracer. To do that create a text file, say packet-tracer.desktop in ~/.local/share/applications/ directory. You can do this by running the following command in Terminal

touch ~/.local/share/applications/packet-tracer.desktop

Open the file with the text editor by running

gedit ~/.local/share/applications/packet-tracer.desktop

Add something like the following to the file and save the file.

[Desktop Entry]
Comment=Launch Cisco Packet Tracer
Terminal=false
Name=Cisco Packet Tracer
Exec=command-to-launch-packet-tracer
Type=Application
Icon=/full/path/to/your/preferred/icon-image
NoDisplay=false


USB microphone (Samson C01U) works, then disappears

Well, I suppose in a way I have solved my own problem.  That is, I wiped my Ubuntu install and installed a fresh 12.04 instance, and now the problem is gone.  I still have the exact same home directory, so presumably it wasn't a user configuration problem.

So apparently the issue was somehow a result of the upgrade.  I hate to have wiped out the problem without finding the cause, but I needed my microphone!


I found a fix:
Basically I added i2400m_usb to /etc/modprobe.d/blacklist.conf and everything mentioned above is gone


does running linux off a usb drive require a proper functioning internal hard disk

No.

Ubuntu will happily run from a USB drive without any other drives present.


It looks like more a problem with a disk than a virus to me.

  It doesn't look like I can. I rebooted it twice, trying it; I bound the function keys to their alternate actions when I first got the computer, so I tried it with and without hitting the Fn key before the F1 key - no soap. I also tried Alt-Ctrl-F1; still nothing. When I relogged into Windows, however, it had me check the disk, using what seems to be a standard procedure. IT found a bunch of errors and said it corrected them; but I still can't log in to Ubuntu.

I don't think you should use Windows to check disk since the partitions in Ubuntu are not NTFS.

You could try to check and fix it using fsck from a Live USB (maybe present in Gparted Live USB).


Keyboard-shortcut to reset the graphic card driver

Since no one has answered this, yet, it shows up at the top of a Google search, try CTRL + ALT + F1 followed by CTRL + ALT + F7.

What has worked for me is just moving my finger on the mouse pad, then once the screen flashes, click the mouse twice.  When that does not work, I use the above.  I did try the various script changes suggested elsewhere, they did not work, which is why I did not repost them.


Syntax Error message with MySQL on the shell

To answer your two questions:

  What kind of software could I use to work with the SQL language (and being more precise when I have an error)?

There are many SQL editors out there.  But since all SQL languages have their own basic nuances by flavor of SQL, let's focus on MySQL specifically.

For MySQL, I use MySQL Workbench (free, Oracle + Community, MySQL only) or DataGrip (not free, 30day trial, from JetBrains - the same company that produces PyCharm, multiple SQL flavors).

That said, they each have their own positive and negative aspects, of which would be a little hard for me to detail fully (and are for the most part out of the scope of what you're asking about from what I can tell).  This pros and cons issue also applies to all editors for SQL and ultimately becomes too broad - so we will focus on he two most common tools I use.

Specifically targeting your question though, neither are going to be "more precise" with the error message - the error message you saw was from the SQL client and server.  These IDEs and tools have their own built in syntax warning systems but they can't stop you from executing a syntactically correct command that doesn't actually work at the DB server itself.  (ALWAYS check your syntax yourself!)

  Is there exists a way to ask the terminal to be more precise?

No there isn't.  It's not the Terminal it's the MySQL client.  It isn't going to be any more precise than the error it gave you (this is why you have to read the queries being entered and syntax check them yourself, even if using a SQL editor/IDE).


Translated with Google Translate:

BROTHER MFC- 7360N to connected USB port for printer configuration Ubuntu 10.04 and following ( localhost ) :

Download drivers at the following addresses ( deb recommended.) : MFC- 7360N # http://welcome.solutions.brother.com/bsc/public_s/id/linux/en/download_prn.html

Install drivers through the Ubuntu repository.

Go to System Settings > Printing .
Click Add, and then specify as device URI : usb :/ / Brother/MFC-7360N serial = EXXXXXXXXXXXXX (with sérial machine located by the screen of the printer in Menu Button > 6 Device Info ? . > 1.No series ( Warning: eg if No. E69719 - series = F2N979180 then serial = E69719F2N979180 think about removing the dash) .
In choosing a driver > Provide PPD file > Select File > File System > usr > share> ppd (you should see a file ppd MFC7360N.ppd ) Select .
Define names for the final configuration and then click apply and print the test page .
Optional: you can specify / dev/usb/lp0 in the location section by double-clicking the printer.

BROTHER MFC- 7360N to connected USB port for printer configuration Ubuntu 10.04 and following ( localhost ) :

Download drivers at the following addresses ( deb recommended.) : MFC- 7360N # http://welcome.solutions.brother.com/bsc/public_s/id/linux/en/download_prn.html

Install drivers through the Ubuntu repository.

Go to System Settings > Printing .
Click Add, and then specify as device URI : usb :/ / Brother/MFC-7360N serial = EXXXXXXXXXXXXX (with sérial machine located by the screen of the printer in Menu Button > 6 Device Info ? . > 1.No series ( Warning: eg if No. E69719 - series = F2N979180 then serial = E69719F2N979180 think about removing the dash) .
In choosing a driver > Provide PPD file > Select File > File System > usr > share> ppd (you should see a file ppd MFC7360N.ppd ) Select .
Define names for the final configuration and then click apply and print the test page .
Optional: you can specify / dev/usb/lp0 in the location section by double-clicking the printer.


Ubuntu 17.10 Server static IP netplan - how to set netmask

Netmask cannot be 255.255.255.1.
Netmask for class C addresses can be:

Prefix size         | Subnet mask
/24                 | 255.255.255.0
/25                 | 255.255.255.128
/26                 | 255.255.255.192
/27                 | 255.255.255.224
/28                 | 255.255.255.240
/29                 | 255.255.255.248
/30                 | 255.255.255.252

Based on this you configuration in .yaml can be

# This file describes the network interfaces available on your system
# For more information, see netplan(5).
network:
  version: 2
  renderer: networkd
  ethernets:
    ens3:
      dhcp4: no
      dhcp6: no
      addresses: [192.168.0.97/25]
      gateway4: 192.168.0.1
      nameservers:
        addresses: [8.8.8.8,8.8.4.4]

Or some appropriate netmask.

Please keep in mind that ip address of host and gateway must be in the same subnet.


Ubuntu SDK, how do I create a tree view in QML?

The ubuntu UI Toolkit has no dedicated treeview component, neither the upstream QtQuick controls have.

But here are few interesting writing about the topic:

http://www.codeproject.com/Articles/632795/QML-TreeModel-and-TreeView
http://qt-project.org/forums/viewthread/30521


I'm not familiar with that particular shell.  Since it supports "help", type help and see if you get lucky and there is an option to run fsck on the unmounted root partition.  If not, you will need to boot from a liveCD and run fsck on it.

Note that if your hard drive is in good shape and you didn't shut the machine down by just removing the power, you should not be seeing these messages.  If you did an orderly shutdown last time, you'll want to run some basic disk drive diagnostics and look at the SMART info on the drive to verify that it's not on it's way out.


"df -h" command puts line breaks in output. How do I fix?

Try: df -Pkh

The P stands for "portable", and will force it to follow POSIX standard output.
I have a hunch will fix any clever formatting that df tries to do.

In the future when you try to solve problems like these, try man df and see if you can find anything that looks like it might work... cause thats what I did =)


@WinEunuuchs2Unix

OP did not ask about Amiance, OP asked for help on 16.10. You don't even ask which desktop or theme is under consideration.

It is a very bad idea to encourage users to edit files in /usr/share/themes.  First, their changes will be lost when the package upgrades. Second, the changes one user, acting as root, might make could be harmful to other users. Third, the same changes can be had by editing files in ~/.config/gtk-3.0.

I think this is a better answer. The format of GTK-3.20 themes has changed. Many themes do not have user-editable files. Furthermore, the CSS style has changed.

The themes provided with gtk-3.20 are

Adwaita
HighContrast
Raleigh
win32

How to customize those things is mostly uncharted waters, but I've got some success.  The gtk.css files provided with those themes are not editable, or not usefully so.  However, you can retrieve the gtk-3.20 source code and in the Adwaita theme, there is a file named gtk-contained.css. That shows the CSS syntax as it is currently used.

Copy as much of that syntax as you want into a file named ~/.config/gtk-3.0/gtk.css.  If you edit the settings in there, then programs that use gtk-3.20 based themes will notice the changes.

The bad news is that the config changes we used to make in Gnome 16.04 no long work because of the change in CSS style in newer GTK-3.20.

But I have verified, but fiddling the settings in here, and then re-starting firefox, that I can alter the color of the scrollbar, add stepper arrows, and so forth.  I don't have great luck fidding with the scrollbar width, a residual frustration of the overlay scrollbar.

But, as soon as you see the syntax difference, you'll see why fiddling themes now is different than it was then.

 scrollbar {
    background-color: #c3c4c4;
    transition: 300ms cubic-bezier(0.25, 0.46, 0.45, 0.94); }
 * {
     -GtkScrollbar-has-backward-stepper: true;
     -GtkScrollbar-has-forward-stepper: true; }
 scrollbar.top {
     border-bottom: 1px solid #9d9d99; }
 scrollbar.bottom {
     border-top: 1px solid #9d9d99; }
 scrollbar.left {
     border-right: 1px solid #9d9d99; }
 scrollbar.right {
     border-left: 1px solid #9d9d99; }
 scrollbar:backdrop {
     background-color: #e1e1df;
     border-color: #a5a5a1;
     transition: 200ms ease-out; }
 scrollbar slider {
     min-width: 30px;
     min-height: 30px;
     margin: -1px;
     border: 4px solid transparent;
     border-radius: 8px;
     background-clip: padding-box;
     background-color: #787c7d; }
 scrollbar slider:hover {
       background-color: #535859; }
 scrollbar slider:hover:active {
     background-color: #2a76c6; }
 scrollbar slider:backdrop {
     background-color: #c3c4c4; }
 scrollbar slider:disabled {
     background-color: transparent; }
 scrollbar.fine-tune slider {
     min-width: 4px;
     min-height: 4px; }
 scrollbar.fine-tune.horizontal slider {
     border-width: 5px 4px; }
 scrollbar.fine-tune.vertical slider {
     border-width: 4px 5px; }
   scrollbar.overlay-indicator:not(.dragging):not(.hovering) {
       border-color: transparent;
       opacity: 0.4;
       background-color: transparent; }
   scrollbar.overlay-indicator:not(.dragging):not(.hovering) slider {
       margin: 0;
       min-width: 3px;
       min-height: 3px;
       background-color: #2e3436;
       border: 1px solid white; }
     scrollbar.overlay-indicator:not(.dragging):not(.hovering) button {
       min-width: 5px;
       min-height: 5px;
       background-color: #2e3436;
       background-clip: padding-box;
       border-radius: 100%;
       border: 1px solid white;
       -gtk-icon-source: none; }
     scrollbar.overlay-indicator:not(.dragging):not(.hovering).horizontal slider {
       margin: 0 2px;
       min-width: 40px; }
     scrollbar.overlay-indicator:not(.dragging):not(.hovering).horizontal button {
       margin: 1px 2px;
       min-width: 5px; }
     scrollbar.overlay-indicator:not(.dragging):not(.hovering).vertical slider {
       margin: 2px 0;
       min-height: 40px; }
     scrollbar.overlay-indicator:not(.dragging):not(.hovering).vertical button {
       margin: 2px 1px;
       min-height: 5px; }
   scrollbar.overlay-indicator.dragging, scrollbar.overlay-indicator.hovering {
     opacity: 0.8; }
   scrollbar.horizontal slider {
     min-width: 40px; }
   scrollbar.vertical slider {
     min-height: 40px; }
   scrollbar button {
     padding: 0;
     min-width: 42px;
     min-height: 12px;
     border-style: none;
     border-radius: 0;
     transition-property: min-height, min-width, color;
     border-color: transparent;
     background-color: transparent;
     background-image: none;
     box-shadow: inset 0 1px rgba(255, 255, 255, 0);
     text-shadow: none;
     -gtk-icon-shadow: none;
     color: #787c7d; }
     scrollbar button:hover {
       border-color: transparent;
       background-color: transparent;
       background-image: none;
       box-shadow: inset 0 1px rgba(255, 255, 255, 0);
       text-shadow: none;
       -gtk-icon-shadow: none;
       color: #535859; }
     scrollbar button:active, scrollbar button:checked {
       border-color: transparent;
       background-color: transparent;
       background-image: none;
       box-shadow: inset 0 1px rgba(255, 255, 255, 0);
       text-shadow: none;
       -gtk-icon-shadow: none;
       color: #2a76c6; }
     scrollbar button:disabled {
       border-color: transparent;
       background-color: transparent;
       background-image: none;
       box-shadow: inset 0 1px rgba(255, 255, 255, 0);
       text-shadow: none;
       -gtk-icon-shadow: none;
       color: rgba(120, 124, 125, 0.2); }
     scrollbar button:backdrop {
       border-color: transparent;
       background-color: transparent;
       background-image: none;
       box-shadow: inset 0 1px rgba(255, 255, 255, 0);
       text-shadow: none;
       -gtk-icon-shadow: none;
       color: #c3c4c4; }
       scrollbar button:backdrop:disabled {
         border-color: transparent;
         background-color: transparent;
         background-image: none;
         box-shadow: inset 0 1px rgba(255, 255, 255, 0);
         text-shadow: none;
         -gtk-icon-shadow: none;
         color: rgba(195, 196, 196, 0.2); }
   scrollbar.vertical button.down {
     -gtk-icon-source: -gtk-icontheme("pan-down-symbolic"); }
   scrollbar.vertical button.up {
     -gtk-icon-source: -gtk-icontheme("pan-up-symbolic"); }
   scrollbar.horizontal button.down {
     -gtk-icon-source: -gtk-icontheme("pan-right-symbolic"); }
   scrollbar.horizontal button.up {
     -gtk-icon-source: -gtk-icontheme("pan-left-symbolic"); }

In my Ubuntu 16.10, I have no Ambiance theme to compare, I don't run Unity. I'll grab a copy of their source and see.

Ah, if a user did want to edit Ambiance gtk-widgets.css as you describe, there is a different format than you describe. Notice the syntax difference in the file /usr/share/themes/Ambiance/gtk-3.20/gtk-widgets.css

/*************
 * scrollbar *
 *************/

.scrollbar,
scrollbar {
    -GtkScrollbar-has-backward-stepper: 0;
    -GtkScrollbar-has-forward-stepper: 0;
}

scrollbar slider {
    background-color: @scrollbar_track_color;
}

.scrollbar.vertical slider,
    scrollbar.vertical slider {
    min-height: 15px;
    min-width: 5px;
}

.scrollbar.horizontal.slider,
scrollbar.horizontal slider {
    min-width: 15px;
    min-height: 5px;
}

.scrollbar.vertical.slider:hover,
scrollbar.vertical:hover slider {
    min-width: 10px;
}

Note the style difference, where the new one has a "." declaration first, followed by an instance name.

The new Ambiance package also does have gtk-3.0/gtk-widgets.css using the old style. It looks like the one you mention. Because version 3.20 is really more like a version 4.00, you can see why there are 2 separate style folders.

I suppose the tricky think is whether some applications are going to differentiate the two things.


Will I be okay if I use USB-stick with 1.87 GB of free space to install Ubuntu 12.10?

If you are trying to make usb bootable and installing ubuntu it will work because ubuntu will be around 700 mb. But if you need to install in it you can't


how to compile the sorcecode of the offical ls.c source code?

ls is part of the coreutils package and as such depends on both other files within coreutils, and the configuration steps. You probably could spend a long time unravelling it from the library but unless you're planning on compiling this a few hundred times a day, I don't think it's worth it.

As pim said in the comments, you can learn about the full build process from the README.hacking file in the root of the git tree. I ran the following without really paying that much heed but this is what worked for me.

sudo apt install git build-essential
sudo apt build-dep coreutils

git clone git://git.savannah.gnu.org/coreutils.git
cd coreutils

./bootstrap  # grabs submodules, sets up configuration
./configure  # does actual compiler configuration

make clean  # remove old attempts
make -j8  # compile using 8 threads (you might want to alter this)

That will compile everything in the src directory and leave the binaries in there. You can run your newly compiled ls with ./src/ls. You can make changes and as long as they're lightweight, you can re-compile them with just the make steps.


Just managed to get it to work:

Suppose your virtual domain is myGuest, your preferred editor is vi, and your guest is installed with grub2and uses systemd. If the last assumption is not true, you might have a look at Working with the serial console.

First, install libguestfs-toolson the host:sudo apt install libguestfs-tools. You will need this when working with headless guests.

Second, shut down your guest: virsh shutdown myGuest.

Next, mount the virtual disk: guestmount -g myGuest -i /mnt (or use any other existing directory as mountpoint). Now in /mnt you should be able to see the filesystem of the guest.

With grub2and systemd, you only have to modify the grub configuration: vi /mnt/etc/default/grub, and modify like

GRUB_CMDLINE_LINUX='console=tty0 console=ttyS0,19200n8'
GRUB_TERMINAL=serial
GRUB_SERIAL_COMMAND="serial --speed=19200 --unit=0 --word=8 --parity=no --stop=1"

As you will have to run update-grubon the guest, for the first start you have to also modify /mnt/boot/grub/grub.cfg. Find the default boot menu item and append the console information to the linuxentry to look similar to

linux   /boot/vmlinuz-4.4.0-75-generic root=UUID=76f3e237-d791-4e9d-8ad7-fe5c9165ae55 ro console=ttyS0,19200 earlyprint=serial,ttyS0,19200

Maybe you need root privileges to mount and edit the files.

Now restart the guest and start the virtual console:

virsh start myGuest && virsh console myGuest

You should see the kernel log and then a login prompt.
After logging in, don't forget to run sudo update-grub.


Why opening a folder via a shortcut makes Audacious to start?

Here is the very subtle fact I had not any vision of. I had used Open with other application... on a folder by a right click to make Audacious enqueu the music files inside of it and start playing them. It must have been one of the times that I had forgotten to remove Remember this application for "folder" files option and the system started to open Audacious every time I tried to mount a drive.
To fix the issue I ordered the system to open folders by Caja and the system is now working perfectly fine.


Problem Installing Ubuntu Alongside Windows 10 Pro

On most laptops and pre-built machines that come with windows 8 and above, they've removed the option to hit a key during post to open the boot menu. In order to get to it now (although I'm sure there's a way to re-enable it) you need to do the following to open the boot menu:
(this is for windows 10)

Go to the Settings menu

Go to the Recovery tab

Under Advanced Startup click Restart Now

Your computer will restart and a menu you pop up instead of the usual login screen

Hit Troubleshoot

Hit Advanced Options

Hit Startup Settings

Hit F10 to get more options

Hit F1 to launch recovery environment, aka the boot menu.

Alternatively, you can use command prompt and type shutdown.exe /r /o to get to that same blue menu

not sure if this is the problem you were having, but hopefully this helps


Serious performance issue only in some applications

The problem was the assistance software "Orca" that for some reason was running in the background. When Orca was removed all is good again.


What do I type in a terminal to understand what commands mean?

What Exactly Are Commands?
A command can be one of four different things:

An executable program like all those files in /usr/bin.
A command built into the shell itself.
A shell function.
An alias.

Identifying Commands
Usually use type to know what a command type is. for example:
$ type cd
cd is a shell builtin

Then this shows that cd command is a builtin command.
Getting help about commands:

help: Get help for shell builtins
--help – Display usage information
man – Display a program's manual page
info – Display a program's info entry
README And other program documentation files

help: Get Help For Shell Builtins
use help for every shell builtin command. try this for example: help cd

--help – Display Usage Information
Many executable programs support a --help option that displays a description of the command's supported syntax and options. For example mkdir --help

man – Display A Program's Manual Page
Most executable programs intended for command line use provide a formal piece of documentation called a manual or man page. For example man mkdir

info – Display A Program's Info Entry
The GNU Project provides an alternative to man pages for their programs, called info. Info pages are displayed with a reader program named, appropriately enough, info. Info pages are hyperlinked much like web pages. For example: info mkdir

README And Other Program Documentation Files
Many software packages installed on your system have documentation files residing in the /usr/share/doc directory. For example: less /usr/share/doc/adduser/examples/adduser.local

**

Briefed from The Linux Command Line book, William E. Shotts, Jr.,
Second Internet Edition

**


How much disk space should I reserve for installing WUBI on Laptop running Window 7?

What are the sizes of your C and D drives? If you open up Computer from the Start Menu, it will show you the sizes and how much is free, e.g. "38 GB free of 100 GB".

I would recommend at least 15GB for Ubuntu, if you are going to be actively using, learning and exploring it.

The version installed by WUBI will be the latest - Ubuntu Precise - 12.04.

WUBI will not slow Windows 7 down -- if you pick Windows 7 from the startup menu, it should start just as fast.

WUBI will install and work just fine whether your Windows is 32-bit or 64-bit.


Can apparmor restrict interpreted languages?

Yes it's possible. It's also in use in Ubuntu, especially on the phone.

To get a basic apparmor script, you can use aa-autodep from the apparmor-utils package.

Quick example for python:

cat >> ~/myapp << EOF
#! /usr/bin/python
EOF

sudo aa-autodep ~/myapp

cat /etc/apparmor.d/home.<user-name>.myapp

This will give you something like:

# Last Modified: Mon Feb 24 18:31:50 2014
#include <tunables/global>

/home/sam/myapp flags=(complain) {
  #include <abstractions/base>
  #include <abstractions/python>

  /home/sam/myapp r,
  /usr/bin/python2.7 ix,

}

Then you can expand on that.


After typing sudo apt update its comes bunch of error like 404 not found

Your Ubuntu installation is correct. This is a 404. /binary-armhf does not exist in that mirror:

I would suggest removing that repo from your apt sources file unless it contains something you need to keep up to date.


Create an unallocated partition for installation of the windows and try. Try Gparted to reallocating the partitions.


Lucid's version of Gnome-Do still has the Docky interface available, and it will act like Gnome-Do when you push the keyboard shortcut for Gnome-Do. You shouldn't even need to have Docky installed separately. The version in Maverick removed the Docky interface. (Both are numbered 0.8.3.1 in the about dialog, however.)

Once you have a version of Gnome-Do without Docky removed (see below), the next thing is to run Gnome-Do. If Gnome-Do doesn't pop up when you run it, summon it with Windows Key + Space. Click the downward-pointing triangle on the top right corner of Gnome-Do and click Preferences. Click on the Appearance tab and select the Docky theme in the drop-down at the top of the tab. You can then configure Gnome-Do just as you would configure Docky.

The versions of the gnome-do packages after 0.8.3.1+dfsg-1ubuntu1 (0.8.3.1+dfsg-2 and 0.8.3.1+dfsg-2ubuntu1) removed the Docky theme. Maverick is also missing the gnome-do-docklets package.

You could download gnome-do and gnome-do-docklets from the Ubuntu Lucid repositories (you could probably still install Maverick's version of gnome-do-plugins with it). It looks like the only fix you'd miss out on is one for crashes caused by GNOME Keyring. I'm not experienced enough to guarantee this will work right, but I'd do it on my own computer. I have at least checked to ensure there aren't any dependency issues.

A surer, but more difficult, approach, would be to build the latest release of gnome-do but reverse the effects of the patch debian/patches/03_disable_docky.dpatch.


I've never used QEMU, but from what I'm seeing on their documentation, it looks like it will create floppy support by default for an x86 architecture machine, even if you don't have a floppy drive in your physical machine.

VMWare and VirtualBox do the same thing. It shouldn't affect performance of the VM unless you're really worried about the VENOM vulnerability. As far as disabling it goes, it looks like the easiest way to disable the floppy drive is to use -nodefaults when opening QEMU.

Otherwise, you should be able to patch the VM to avoid the VENOM vulnerability, but I don't think it will disable the floppy. Here's a link with more information on the vulnerability.


How to disable a program in "Startup Applications" via command line

You need to copy the file into ~/.config/autostart/ and then edit that new file, changing the X-GNOME-Autostart-enabled value from true to false.


Error in downloading Packages e.g. VLC media player

In the terminal, type sudo apt-get install -f. This attempts to fix broken dependancies.


Snap install of "instagraph" works but can't log in even after changing password

Read your error messages! The first few:

Gtk-Message: Failed to load module "gail"
Gtk-Message: Failed to load module "atk-bridge"
Gtk-Message: Failed to load module "canberra-gtk-module"
Qt: Session management error: None of the authentication protocols
specified are supported
OffscreenRenderer::OffscreenRenderer(QObject*)
QNetworkManagerInterface::QNetworkManagerInterface(QObject*)
propsReply "An AppArmor policy prevents this sender from sending this
message to this recipient; type=\"method_call\", sender=\":1.663\" (uid=1000 pid=19917

Should tell you that you're missing some authentication modules ( gail, atk-bridge, canberra-gtk-module), and that later attempts at authentication will fail ("Qt: Session management error: None of the authentication protocols specified are supported").

Subsequent error messages, like:

QNetworkManagerInterface::QNetworkManagerInterface(QObject*)
    propsReply "An AppArmor policy prevents this sender from sending this
    message to this recipient; type=\"method_call\", sender=\":1.663\" (uid=1000 pid=19917

Are just the results of failing authentication, propagating through instagraph startup.

This question has been seen before, and has a well-liked answer here.


How to install PhpStorm in Ubuntu 14.04 LTS?

Instructions here: https://web.archive.org/web/20161207101644/http://sysads.co.uk:80/2014/08/08/install-phpstorm-7-on-ubuntu-14-04/

Please note that PhpStorm is not FREE, this is a 30-day trial!

Install dependencies

sudo apt-get purge openjdk*
sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo apt-get install oracle-java8-installer oracle-java8-set-default

Install PhpStorm

wget http://download-cf.jetbrains.com/webide/PhpStorm-2017.1.4.tar.gz
tar -xvf PhpStorm-2017.1.4.tar.gz
cd PhpStorm-171.4694.2/bin/
./phpstorm.sh


Hi mire12 and welcome to Ask Ubuntu. I hope you find the site useful and continue to use Ubuntu for years to come!
If you take a look at Docker's Installation Page you'll see that in order to configure the repository you are going to install docker from you'll run:
sudo add-apt-repository \
   "deb [arch=amd64] https://download.docker.com/linux/ubuntu \
   $(lsb_release -cs) \
   stable"

If you look closely you'll see the command lsb_release -cs is run. If you try and execute that on your machine you'll get the distribution's codename. For Ubuntu 20.10 that would be groovy as the release's name is Groovy Gorilla (really cool release name if you ask me :P). I'm not 100% sure this is what you'll get as I haven't updated yet though... Either way, I'm certain the output of lsb_release -cs is none of focal (20.04), bionic (18.04), or xenial (16.04) which are the ones docker currently supports.
Then, if you run the sudo add-apt-command you'll be adding the following repo: deb [arch=amd64] https://download.docker.com/linux/ubuntu groovy stable
This doesn't exist as docker only supports the three releases I listed before.
You then have two options.

The first one is to wait until they release a docker version for 20.10. I'm not sure if they will do so and if they do I don't know how long it'll take.

You can manually run the command swapping lsb_release -cs for focal to use the docker version for Focal Fossa. This doesn't guarantee compatibility but I have done it some other times and it worked out fine. If you try to walk down this road you'll then have to run:

sudo add-apt-repository \
   "deb [arch=amd64] https://download.docker.com/linux/ubuntu \
   focal \
   stable"

I hope this works out for you! If it doesn't you could also try to manually download the .deb file for docker and install that with dpkg. You can read more on that on the page I linked at the beginning (i.e. this one :P)
P.D:
The $() structure used in the add-apt-repository command is called a Command Substitution in Bash's lingo. What it's basically doing is replacing the whole $() structure with the output of whatever is within the brackets. In our case that amounts to replacing $(lsb_release -cs) with groovy. That's why manually fixing a release codename is a feasible workaround.
You can read more on Command Substitution on Bash's manpage which you can read by running man bash if Bash is installed. It's the default shell on Ubuntu so chances are it's the one you commonly use. The manpage is worth a read; I learned a lot by doing so :P. I'm citing a bit on Command Substitution explaining the above from the manpage so that you don't have to comb through it:
Command Substitution
       Command substitution allows the output of a command to replace
       the command name.  There are two forms:

              $(command)
       or
              `command`

       Bash performs the expansion by executing command and replacing
       the command substitution with the standard output of the command,
       with any trailing newlines  deleted.
       Embedded newlines are not deleted, but they may be removed during
       word splitting.  The command substitution $(cat file) can be
       replaced by the equivalent but faster $(< file).

You can also read it online here but I find reading manpages on a terminal emulator to be more appealing. I love the old-schooly vibe it has :P


The text below was obtained from the nixCraft page Linux: Should You Use Twice the Amount of Ram as Swap Space?. (Please follow the link and read the source for more information)

Note that nixCraft page cites text purportedly coming from the OpenBSD FAQ, but there is no matching text in the current document; this may however be something that used to be in there in 2006 (so the 2 x RAM rule was already obsolete more than 10 years ago):

  Nonsense rule: Twice the size of your main system RAM for Servers

  According to OpenBSD FAQ:

    Many people follow an old rule of thumb that your swap partition
    should be twice the size of your main system RAM. This rule is
    nonsense. On a modern system, that's a LOT of swap, most people
    prefer
    that their systems never swap. You don't want your system to ever
    run
    out of RAM+swap, but you usually would rather have enough RAM in the
    system so it doesn't need to swap.

More from the nixCraft page:

  Red hat recommends setting as follows for RHEL 5:

    The reality is the amount of swap space a system needs is not really
    a
    function of the amount of RAM it has but rather the memory workload
    that is running on that system. A Red Hat Enterprise Linux 5 system
    will run just fine with no swap space at all as long as the sum of
    anonymous memory [memory mapping without file or device backing it:   memory obtained from the OS stack and heap] and system V shared memory is less than about 3/4 the
    amount of RAM. In this case the system will simply lock the anonymous
    and system V shared memory into RAM and use the remaining RAM for
    caching file system data so when memory is exhausted the kernel only
    reclaims pagecache memory.

    Considering that:
    1. At installation time when configuring the swap space there is no easy way to predetermine the memory a workload will require, and
    2. The more RAM a system has the less swap space it typically needs, a better swap space [might be along this recommendation for CentOS Linux 7.x and RHEL 7]:

And so the nixCraft page concludes:

  Conclusion

  If Linux kernel is going to use more than 2GiB swap space at a time,
  all users will feel the heat. Either, you get more RAM (recommend) and
  move to faster storage to improve disk I/O. There are no rules, each
  setup and configuration is unique. Adjust values as per your
  requirements. Select amount of swap that is right for you.

Furthermore, this Red Hat article: Do we really need swap on modern systems? (2017) says:

  Our size recommendation for most modern systems is ‘a part of the
  physical RAM’, for example, 20%. With this, the painfully slow phase
  of operation in our example will not last as long, and the OOM kicks
  in earlier.

  Of course, there are scenarios when different behaviour is desired.
  When aware of the behaviour, such swap configurations are ok, as well
  as running the system without any swap. Such a system is supported by
  us as well - but the customer should know the behaviour in the above
  situations.


How to disable live window resizing in Trusty Tahr

You'll have to install CCSM: sudo apt-get install compizconfig-settings-manager.

Launch it with ccsm and go to Window Management and click Resize Window.

Select General tab and change Default resizing mode from Normal to Rectangle.

Sorry for the display language but it won't run with export LANG=en_US.


After using the sudo apt-get remove --purge to uninstall the software then, you can use sudo apt-get autoremove to get rid of the residing none-useful files.


When will we see Ubuntu smartphones in shops and/or on ebay?

From the Ubuntu Insights blog post by Richard Collins, Ubuntu Product Management, Get the FAQs about Ubuntu on smartphones:

"When will it be available to buy?

This depends mainly on our partners’ roadmaps, but we are working with these partners today and expect the Ubuntu to be available on phones during 4th quarter 2013 or in early 2014."


Licence Error for Matlab 2012a on Ubuntu 12.04 (64-bit)

In this case I would try creating the directory the license should be written to. Open a terinal with Alt-Ctrl-T and enter:

sudo mkdir -p /usr/local/MATLAB/R2012a/licenses
sudo chmod a+rw  /usr/local/MATLAB/R2012a/licenses

The first two of these may already exist, and if so that's OK, just go on. Then try the license install again.


To enable printing from both the host Ubuntu and the guest Windows your best choice is to share that printer via your network (which then would be the internal network localhost between the host and the guest).

Make sure that printer sharing was enabled

Search for printers in the Windows settings. Click on The printer I want isn't listed:

Tick select a shared printer to give in the network name directly or Browse to find the network your printer is attached to:

Select the appropriate network printer:

Windows may need additional drivers for printing.


Okay,i find the workaround. It seems like i was having the error : Incompatible namespaceIDs. I found a work around  here . So well it finally got solved.

If you are also having the same problem for  Incompatible namespaceIDs, try the following, it worked like a charm for me. Leave comments if you still have problems and I will get back to you.

Solution :
1. Stop the problematic DataNode(s).
2. Edit the value of namespaceID in ${dfs.data.dir}/current/VERSION to match the corresponding value of the current NameNode in ${dfs.name.dir}/current/VERSION.
3. Restart the fixed DataNode(s).   That will solve the problem for you.


Is it possible to replace the Unity launcher?

It will certainly be possible to continue with whatever setup you use now. (Not use Unity, but a different dock.)

However whether it will be possible to use the rest of the Unity interface alongside a different dock remains to be seen. With current Unity (10.10) that is not possible.


Ubuntu can't connect to WPA2 but dual-booted Windows can

Yes,I think it's a Ubuntu driver problem in managing the WEP/WPA2. Try to do a test disabling your WiFi protection to check if this is the problem. Try also with other WiFis, maybe it's a problem of your own router.


Tiling windows horizontally and vertically under Lubuntu (LXDE/Openbox)?

Configuration:

Yes, you can achieve this by adding a few custom keyboard shortcuts to your openbox configuration file.

Open your rc.xml variant (e.g. ~/.config/openbox/lxde-rc.xml, ../lubuntu-rc.xml or ../rc.xml) and insert the following snippet within the <keyboard>..</keyboard> section:

<!-- Vertical tiling -->
<keybind key="C-W-v">
  <action name="UnmaximizeFull"/>
  <action name="MoveResizeTo">
    <width>50%</width>
  </action>
  <action name="MaximizeVert"/>
  <action name="MoveResizeTo">
    <x>0</x>
    <y>0</y>
  </action>
  <action name="NextWindow">
    <interactive>no</interactive>
    <dialog>none</dialog>
    <finalactions>
      <action name="UnmaximizeFull"/>
      <action name="MoveResizeTo">
        <width>50%</width>
      </action>
      <action name="MaximizeVert"/>
      <action name="MoveResizeTo">
        <x>-0</x>
        <y>0</y>
      </action>
    </finalactions>
  </action>
</keybind>

<!-- Horizontal tiling -->
<keybind key="C-W-h">
  <action name="UnmaximizeFull"/>
  <action name="MoveResizeTo">
    <height>50%</height>
  </action>
  <action name="MaximizeHorz"/>
  <action name="MoveResizeTo">
    <x>0</x>
    <y>0</y>
  </action>
  <action name="NextWindow">
    <interactive>no</interactive>
    <dialog>none</dialog>
    <finalactions>
      <action name="UnmaximizeFull"/>
      <action name="MoveResizeTo">
        <height>50%</height>
      </action>
      <action name="MaximizeHorz"/>
      <action name="MoveResizeTo">
        <x>0</x>
        <y>-0</y>
      </action>
    </finalactions>
  </action>
</keybind>

<!-- Restore window dimensions -->
<keybind key="C-W-r">
  <action name="UnmaximizeFull"/>
  <action name="NextWindow">
    <interactive>no</interactive>
    <dialog>none</dialog>
    <finalactions>
      <action name="UnmaximizeFull"/>
    </finalactions>
  </action>
</keybind>

Shortcuts in action:

Usage:

Super+Ctrl+V: Tile last active windows vertically
Super+Ctrl+H: Tile last active windows horizontally
Super+Ctrl+R: Restore original window dimensions

To modify these assignments simply edit the <keybind key="..."> lines in the snippet above.

Notes:

This method will only tile the two last active windows
You can swap window positions by focussing the inactive window and pressing the hotkey again


HDMI Audio not working on fresh Dell install

PulseAudio volume control fixed the issue.

sudo apt-get install pavucontrol


How can I play content from a media server?

You need to install the package totem-plugins-extra. You can find it in the Software Centre or just use:

sudo apt-get install totem-plugins-extra

from the command line.

Now open Totem, go to Edit -> Plugin, check that the coherence plugin is installed.

In the dropbox of the sidebar select Coherence DLNA/UPnP Client. You should be able to browse your server from there.

You can find more info in the totem plug-ins webpage.


Apt/Synaptic needs to reinstall package but can't find the archive for it

Well we may need a few steps to fix this.

Start with:

sudo dpkg --remove --force-all hl1440lpr

If that fails:

sudo rm -i /var/lib/dpkg/info/hl1440lpr.*
sudo dpkg --remove --force-remove-reinstreq hl1440lpr

Confirm Apt is fixed. The following command should return no errors:

sudo apt-get update


you could install gshare.

with it you can select what folders you want to share just by right clicking them.

sudo apt-get install gshare

Here is my home folder that I share in my local network.


You will need to set up your USB boot device to boot in UEFI mode, unless you really want to reset your machine to compatibility mode each time you boot it.  The USB will need an EFI partition (FAT32, 300M, flagged bootable) with the bootloaders grubx64.efi and shimx64.efi in /EFI/Boot, with the bootloader to run (shim for secure boot, grub for non-secure) renamed to bootx64.efi.  You could have both boot mechanisms, like the live media does.  You can just copy the bootloaders into the EFI filesystem if you want (or if the installer does not put them into the right place (and on removable media, that is likely, using the /EFI/ubuntu directory just like on the hard disk).
  Once you get grub running, then you will need to deal with any video problems.
Some old UEFI machines with H2o may have problems with secure boot, but those issues in the Toshibas have been fixed 18 months ago, so always good to use the current firmware from the vendor.


WD 3TB external HD that is not recognized by Ubuntu 14.04 (the BIOS does support +2.2TB drives)

The issue was solved after I accessed the drive from a Windows computer. Just that.

I've inserted it again on my linux machine and it works normally, as it should.

Just in case it helps someone, some day.


I don't think this can be done.
To select a non-default boot action, you will need network connectivity before the system boots!
A workaround is to let all three computers A, B, C, boot into the default, say Ubuntu 64bit. This can be done with wake-on-LAN. Once fully booted, you can SSH into Computer C and use:
`grub-reboot $1`

command to reboot Computer C to 32bit Ubuntu. Here $1 is the menuentry number in the grub, that starts from 0 for the first entry.
Reference:
How to enable Wake On Lan (WOL) in Ubuntu 16.04
How can I get grub2 to boot a different option only on the next boot?
There may be another way
If your computers A B and C all meet the hardware requirements for Intel's Active Management Technology (AMT) then it may be possible to access BIOS (and thus possibly GRUB) through LAN while the system boots.
I don't know anything about it, and the How-To I saw is for Windows. Here is some information about AMT and Linux. In any case such a solution would not be Ubuntu specific.
Hope this helps


Unable to connect via MySQL Workbench to localhost in Ubuntu 16.04 (passwordless root)

The issue is likely due to socket authentication being enabled for the root user by default when no password is set, during the upgrade to 16.04. This important caveat is documented in the 16.04 release notes:

  Password behaviour when the MySQL root password is empty has changed.
  Packaging now enables socket authentication when the MySQL root
  password is empty. This means that a non-root user can't log in as the
  MySQL root user with an empty password.

For whatever reason, the MySQL Workbench that came with 16.04 doesn't work out of the box with MySQL server, at least for me. I tried using "Local Socket/Pipe" to connect in a number of different ways but to no avail.

The solution is to revert back to native password authentication. You can do this by logging in to MySQL using socket authentication by doing:

sudo mysql -u root

Once logged in:

ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY 'password';

which will revert back to the native (old default) password authentication. If you've attempted some other method to fix the issue, you'll want to make sure the "plugin" field in mysql.user is set to "auth_token", which may require using mysqld_safe to log in to MySQL in the event you've been tinketing with things, like I did.

Credit to Miguel Nieto's blog post for this solution.


White blocking screen when put youtube in full-screen mode

If you don't use Chrome, ignore this answer.

If you use Chrome, the problem doesn't come frome Flash "as it" but the PPAPI library used by Chrome and Adobe, developping together PepperFlash (/opt/google/chrome/PepperFlash/libpepflashplayer.so).

You can desactivate it, so Chrome will use the NPAPI, like other navigators (you must have flashplugin : sudo apt-get install flashplugin-installer)

1) Open Chrome and type in the omnibox (the URL bar) :

chrome://plugins/

2) Press "+ details" in the top-right corner of the page.

3) Scroll down to Adobe Flash Player

4) Find the Type: PPAPI line

5) Click on "disable" right below that line.

Restart Chrome and try a full-screen flash video again.


No audio input device on ubuntu 13.10 with front-mic plugged-in

I would try 2 things:

Unplugging and plugging the microphone.
try restarting pulseaudio with killall pulseaudio in terminal


Is it possible to access disks in an LVM after a reinstallation of the OS on a separate drive?

yes, as you can verify by building a small test diskset (for example by combining a handfull of files) and accessing it lateron from another installation or even a live CD / USB stick / whatever.
Don't forget to install the lvm2 package to the installation you want to use, if it isn't already present.

as root (or with sudo)

apt-get install lvm2
pvscan will show if the physical volume is detected
vgscan searches for the volume group
modprobe dm-mod to load the module
vgchange -ayto activate the volumes
lvscan should now show the logical volumes as active and mountable

see also: how to move volume group to another system

I'd also recommend to use vgfcbackup to backup the configuration info of your volume group.