drush arr (drush archive-restore) says: Missing required argument: file I have been requested, against my better advice, to try to ensure that a Drupal site for an associated part of our organisation is up to date, although the site developers left no admin maintenance documentation nor information about any custom setup that they may have done, and now seem to be uncontactable (poor project management on the part of the site owners).
The standard Drupal update did not work, and I now have to try to revert the site back from the drush archive that was taken just beforehand.
However, drush arr (drush archive-restore) says:

Missing required argument: file.

I'm not sure what file I need to specify (our own installation of Drupal is somewhat customised and clear upgrade instructions, working in a different way, are supplied by the maintainers).
Looking in the drush-backups folder, I seem to have two choices:
/root/drush-backups/archive-dump/20200831154526/sitename.20200831_154526.tar.gz
/root/drush-backups/sitename/20200831154744/drupal/

(the latter of which seems to contain the Drupal files as-is (not as a .tar.gz file))
Is the .tar.gz file from the archive-dump folder the file that drush arr is wanting, and then drush will know how to find the rest automagically?
drush arr is expecting a site archive file as an argument. Its sibling drush command,drush ard, creates a site archive file. (see the drush codebase for more details on how this command works) The /root/.../drupal/ path is a backup drush creates when you run drush up
The /root/drush-backups/archive-dump/ path matches the format of drush ard's default output but if you didn't create this archive file you should inspect it (tar -tvf) to confirm it has the code/files/DB backup within it.
So yes, drush arr will restore from a site backup but you should take necessary precautions since you've inherited an undocumented process.