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When trying to add my user to a new group to run an application (Kismet), I accidentally made it the ONLY group my user is in. I had run the groups command and saw seven or so other groups I was in, but when I logged out and logged back in to save my changes those other groups are gone.

I have root access, but my bash history doesn't show output.

How do I find out what groups I was in? I know how to add myself back to them, just not how to figure out what they were.

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    Backup copies of /etc/group? Find files you own that have gids not equal to kismet?
    – Jeff Schaller
    Commented Dec 18, 2016 at 3:34
  • The files thing is a clever idea, I ended up listing default groups and restoring those. Hoping I don't run into crazy access issues in the future now... Commented Dec 18, 2016 at 3:36

2 Answers 2

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I had searched around previously, but just found this answer which basically solves my needs: Default groups for user in Ubuntu?

  1. Login as root (because I was removed from sudoers group):

    su - root

  2. List the setup log from creating my user

    grep user-setup /var/log/installer/syslog

  3. Then I ran the command (using the list of groups from the above command)

    usermod -a -G adm,cdrom,lpadmin,sudo,sambashare,dip username

  4. Log out and back in, done!

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If you're still logged in anywhere, you can run the command groups to list the groups that the running process is in. If you're logged in on a terminal that you don't have access to, or more generally if you have a program running somewhere from before the group change, you can list that process's groups with ps -o rgroup,supgrp 1234 where 1234 is the process ID (that's for Linux, the syntax may be different on other Unix variants).

Whenever you change something about your account, it's a good idea to remain logged in and try logging in in another terminal to validate the change!

If you used vigr or some sufficiently compatible tool, it leaves a backup in /etc/group-. This does not apply to all tools, for example the addgroup command on Debian doesn't make a backup. Make a copy of the backup before editing the file again, otherwise it'll be overwritten.

It's a good idea to make frequent backups of /etc. I recommend using etckeeper (available on most Linux distributions) to keep a full history under version control (etckeeper automatically before and after installing packages, but you should commit all changes manually anyway with a meaningful log message).

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    "Whenever you change something about your account, it's a good idea to remain logged in and try logging in in another terminal to validate the change!" << Great advice, this would've prevented the issue. I also didn't know where to backup the list. Commented Dec 19, 2016 at 5:54

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