How to add group to a user without removing other group in suse linux with usermod?

Question

I have one user, which has one primary group & one secondary group, like:

[ testuser Welcome ~ ]$ id

uid=2000(testuser) gid=2000(testuser) groups=2000(testuser),27(sudo),2001(testgroup)

Primary group is testuser & secondary group is testgroup.

Now, I try to add one more secondary group testgroup2 to that user with below command

usermod -G testgroup2 testuser

but it removed the previous secondary group (testgroup) & added the new one. My need is that previous secondary group should not be removed & the new secondary group should be added.

I saw in ubuntu, there is one option like -a which can append the group to user without removing the other group.

Please let me know is it also possible on suse linux or not...?

Thankx !!!

Answer 1

In SLES11 SP3, the usermod command (from pwdutils 3.2.15) supports a -A option that will do what you want:

-A, --add-to-group group,...
    With this option a list of  groups can be specified, which the user should
    become a member of. Each group is separated from the next one only by a comma,
    without whitespace.

In SLES12 and OpenSUSE 13.1, the usermod command (from the more widely-used shadow-utils 4.1.5.1) supports a -a option to be used in conjunction with the -G option:

-a, --append
    Add the user to the supplemental group(s). Use only with -G option.

-G, --groups GROUP1[,GROUP2,...[,GROUPN]]]
    A list of supplementary groups which the user is also a member of. Each group
    is separated from the next by a comma, with no intervening whitespace. 

    If the user is currently a member of a group which is not listed, the user
    will be removed from the group. This behaviour can be changed via the -a option,
    which appends the user to the current supplementary group list.

Answer 2

If your usermod has no way to append (not even -A), try tacking on the current set of groups:

usermod -G "$(groups testuser | sed 's/.*: //;s/ /,/g'),testgroup2" testuser

Answer 3

This command makes you specify a list of all groups, it replaces the old ones.

 -G, --groups GROUP1[,GROUP2,...[,GROUPN]]]
           A list of supplementary groups which the user is also a member of. Each group is separated from the next by a comma, with no intervening whitespace. The groups are subject to the same restrictions as the group given with the -g option.

Instead use adduser:

adduser [options] user group

adduser can be used to add a user, but also to add a user to a group.

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or as @mark plotnick points out, use the -a option of usermod