I have a user 'Peter' with primary group 'users'. I want to change his primary group from 'users' to 'nogroup' with However, what the command did was to add 'nogroup' to Peter as a secondary group. Is there any way to change a user's primary group after the userid's creation?

Thanks.

You probably meant -g. man usermod.

This command assigns nogroup as the primary group of printuser, which is what I want, but it also demote the original primary group 'users' to be the secondary group.

Is there a command to assign 'nogroup' as the new primary group with no secondary group?

Thanks !

After you change the primary group for user successful, then issue:

usermod -G <the_only_primary_group> <user>

I've tried a variety of all of these, and I must warn others - be careful.

The following command will change a user's primary group. All set?

Unfortunately, this will also remove any other group associations the user had. One can quite easily remove all of one's superuser access with this command.

If you simply want to add a user to a supplementary group (retaining existing groups) run this.

The -a is a recent addition, allowing for the retention of existing groups. You could go into /etc/passwd and change the group id associated with the user. This didn't work for me even after restarting the shell. The command that worked perfectly for me, was quite easily:

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