[SOLVED] groupmems vs /etc/passwd primary group

scriptkiddy · 02-29-2016, 02:25 AM

I added a few users to the users group "test1" "test2" and "test3" and set their primary group to users using following:

Code:

# usermod -g users test1
# usermod -g users test2
# usermod -g users test3

I then decided to create a new group and just add one user to it:

Code:

# groupadd gamers
# usermod -a -G gamers test1

Using groupmems, I checked to see who had gamers as their primary group:

Code:

# groupmems -l -g gamers
test1

I'm confused here because groupmems is supposed to show primary group memberships, so why is test1 showing, it should return nothing (I'm also confused on the syntax as groupmems --help indicates that the usage should be groupmems -g groupname -l...

Here is the result of users group:

Code:

# groupmems -l -g users
 test1  test2  test3

So test1 has two primary groups?

So I checked /etc/passwd

Code:

# more /etc/passwd | grep test1
test1:x:1001:100::/home/test1:/bin/bash

And it shows that the gid is 100 (users) which is in fact the primary group...

So which is right, groupmems or /etc/passwd, or does /etc/passwd simply showing the "first assigned" primary group vice the primary group? In any case how can a user have more than one primary group?

Please help me understand.

SK

pan64 · 02-29-2016, 02:33 AM

user's cannot have more than one primary group. see /etc/group to check membership.

taea00 · 02-29-2016, 08:36 AM

As pan64 said, users cannot have more than one primary group. You can run the "groups" command on a user to see what their groups are. Primary is listed first, secondary groups are after that.

I think you might be getting confused with the groupmems command though. Check the man page for groupmems with "man groupmems" and it will show you that -g is they group you're checking and -l is listing the users in that group. It isn't specifying primary or secondary groups.

I've never heard of groupmems before so I thank you for that interesting new command.

scriptkiddy · 03-01-2016, 12:14 AM

Thanks for the replies. I agree a user cannot have more than one primary group which is why I was confused when I saw groupmems' output.
I think I'll just stick to groups (also new command for me). It seems to list the primary, then the supplementary groups, so that was easy, and the command is simpler than groupmems.

Many thanks for the insights and thoughts.

SK