Q: Trouble verifying download of openSUSE Tumbleweed image When I try using sha256sum to verify the openSUSE Tumbleweed image I just downloaded, I get an error:
sha256sum: openSUSE-Tumbleweed-DVD-x86_64-Snapshot20170521-Media.iso: No such file or directory
openSUSE-Tumbleweed-DVD-x86_64-Snapshot20170521-Media.iso: FAILED open or read
sha256sum: WARNING: 14 lines are improperly formatted
sha256sum: WARNING: 1 listed file could not be read

I have verified that the image and the checksum are in the same directory, I have verified that they have the same name (except for the ".sha256" at the end of the checksum file), and I have verified that I downloaded the correct checksum for my image.

A: The problem is in the checksum file itself. If you open the file in vi, you'll see the problem:
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

c8206b18c4ee07b09807a60b653b7e3956d86002b7609f20ab63c9549049796b  openSUSE-Tumbleweed-DVD-x86_64-Snapshot20170521-Media.iso
-----BEGIN PGP SIGNATURE-----
...

The issue is the name of the file that the checksum expects to find. Change the name of the file on line 4 to match the name of the image you downloaded:
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

c8206b18c4ee07b09807a60b653b7e3956d86002b7609f20ab63c9549049796b  openSUSE-Tumbleweed-DVD-x86_64-Current.iso
-----BEGIN PGP SIGNATURE-----
...

Then just run the sha256sum command again and it should work. The expected output from the sha256sum command is similar to this:
$ sha256sum -c openSUSE-Tumbleweed-DVD-x86_64-Current.iso.sha256
openSUSE-Tumbleweed-DVD-x86_64-Current.iso: OK
sha256sum: WARNING: 14 lines are improperly formatted

Whoever uploaded the new signature forgot to change the expected file name to the current image name. The issue is more easily caught if you download the checksum file from the browser. If you download from a browser, the file will be named openSUSE-Tumbleweed-DVD-x86_64-Snapshot20170521-Media.iso. However, if you download it with wget or something similar, the file name will be named openSUSE-Tumbleweed-DVD-x86_64-Current.iso like you would expect, thus obfuscating the issue.
