In this tutorial, you will learn how to set environment variables in Linux for a single user and globally. You will also learn how to list all environment variables and how to unset (clear) existing environment variables.
Environment variables are commonly used within the Bash shell. It is also a common means of configuring services and handling web application secrets.
It is not uncommon for environment specific information, such as endpoints and passwords, for example, to be stored as environment variables on a server. They are also used to set the important directory locations for many popular packages, such as JAVA_HOME for Java.
Setting an Environment Variable
To set an environment variable the export command is used. We give the variable a name, which is what is used to access it in shell scripts and configurations, and then a value to hold whatever data is needed in the variable.
For example, to set the environment variable for the home directory of a manual OpenJDK 11 installation, we would use something similar to the following.
To output the value of the environment variable from the shell, we use the echo command and prepend the variable’s name with a dollar ($) sign.
And so long as the variable has a value it will be echoed out. If no value is set then an empty line will be displayed instead.
Unsetting an Environment Variable
To unset an environment variable, which removes its existence all together, we use the unset command. Simply replace the environment variable with an empty string will not remove it, and in most cases will likely cause problems with scripts or application expecting a valid value.
To following syntax is used to unset an environment variable
For example, to unset the JAVA_HOME environment variable, we would use the following command.
Listing All Set Environment Variables
To list all environment variables, we simply use the set command without any arguments.
An example of the output would look something similar to the following, which has been truncated for brevity.
BASH=/bin/bash BASHOPTS=checkwinsize:cmdhist:complete_fullquote:expand_aliases:extglob:extquote:force_fignore:globasciiranges:histappend:interactive_comments:login_shell:progcomp:promptvars:sourcepath BASH_ALIASES=() BASH_ARGC=(="0") BASH_ARGV=() BASH_CMDS=() BASH_COMPLETION_VERSINFO=(="2" ="8") BASH_LINENO=() BASH_SOURCE=() BASH_VERSINFO=(="5" ="0" ="3" ="1" ="release" ="x86_64-pc-linux-gnu") BASH_VERSION='5.0.3(1)-release' COLUMNS=208 DIRSTACK=() EUID=1000 GROUPS=() HISTCONTROL=ignoreboth HISTFILE=/home/ubuntu/.bash_history HISTFILESIZE=2000 HISTSIZE=1000 HOME=/home/ubuntu HOSTNAME=ubuntu1904 HOSTTYPE=x86_64 IFS=$' \t\n' LANG=en_US.UTF-8 LESSCLOSE='/usr/bin/lesspipe %s %s' LESSOPEN='| /usr/bin/lesspipe %s' LINES=54
Persisting Environment Variables for a User
When an environment variable is set from the shell using the export command, its existence ends when the user’s sessions ends. This is problematic when we need the variable to persist across sessions.
To make an environment persistent for a user’s environment, we export the variable from the user’s profile script.
- Open the current user’s profile into a text editor
- Add the export command for every environment variable you want to persist.
- Save your changes.
Adding the environment variable to a user’s bash profile alone will not export it automatically. However, the variable will be exported the next time the user logs in.
To immediately apply all changes to bash_profile, use the source command.
Setting Persistent Global Environment Variables
When an environment variable needs to persist globally across the entire system, we can set it in the default profile loaded by all users on the system.
All global profile settings are stored under /etc/profile. And while this file can be edited directory, it is actually recommended to store global environment variables in a directory named /etc/profile.d, where you will find a list of files that are used to set environment variables for the entire system.
- Create a new file under /etc/profile.d to store the global environment variable(s). The name of the should be contextual so others may understand its purpose.
sudo touch /etc/profile.d/http_proxy.sh
- Open the default profile into a text editor.
sudo vi /etc/profile.d/http_proxy.sh
- Add new lines to export the environment variables
- Save your changes and exit the text editor