OpenSolaris: Remove user from a group from command line

Question

How can I remove a user from a group from the command line in OpenSolaris (2008.11)?

I know I can define a user's primary group and a add a user to a group with:

usermod -g primarygroup user
usermod -G group_list user

What's the corresponding command to undo that action and remove a user from the group without just editing /etc/groups

Answer 1

You could try something like this:

usermod -G "" username

That should remove them from the extra group. This appears to work in SOL10/OSOL/Linux. It's worth noting that'll remove them from ALL extra groups. If you want to just remove them from one just get their current groups list:

id username

and then just build the list of extra groups to add with usermod -G and don't add the one you want to take them out of.

Answer 2

The following answer applies to Debian, but maybe it will work on OpenSolaris as well.

Run usermod -g another_group user (modifies /etc/passwd), and/or run usermod -G group_list user (modifies /etc/group).