Problem with group membership

[unixnewbie]

Hi,
I used the following command to change the secondary group of a particlar user.
/usr/sam/lbin/usermod.sam -F -G 4000 .
Now my question is whether this command will remove all other secondary group membership for that particular user or it will add the group with ID 4000 as another secondary group for the user ?

[Jeff_Traigle]

It replaces any existing secondary group memberships with what you specify.

[TTr]

Run the command "groups " and you will see all the groups that the login-id belongs to. Apparently when /usr/sbin/usermod is called from within sam, does exactly that.

[unixnewbie]

Thanks Jeff, Could you tell me the otion to add one more secondary group to a user using usermod.sam ?

[UVK]

usermod -G

this is modify the secondary groups for a particular user.

[Mel Burslan]

usermod utilities are very temperamental and may or may not work at any given time. Easiest way to do this I generally use, is, edit the /etc/group file, find the group you want to add this user to, go to the end of the line and type a "," (comma) immediately follwed by the userid, no spaces or nothing else. Just follow one of the other groups in the same file for the proper format.

Word of caution, the format of the file is strict and a typo may make life miserable for other and in turn for you, but again, we are all unix admins and should know what to do. Right ? :)

[unixnewbie]

My problem is the users I am trying to change group membership is oracle related and root. Usermod command will not work on users that are already logged in and it is difficult to get user like oracle logged off. Thats why I want to use /usr/sam/lbin/usermod.sam which will work on users that are currently logged in.

[unixnewbie]

Thanks Mel for the input. Yes editing the /etc/group file was the easiest way and would have been quicker given the fact that i did this on a number of users. Still my question about the option to do it in command line remains..

[Mel Burslan]

cat /etc/group | sed -e "/^dba/s/$/,newuser/" > /var/tmp/dummygroup
cat /var/tmp/dummygroup > /etc/group

this adds the secondary group membership for "dba" group, to the userid "newuser"

you can script these two commands as your heart desires.

hope this helps

[Jeff_Traigle]

Using TTr's reference to the groups command, you could do this to add a secondary group without eliminating current memberships:

CUR_GROUPS=$(groups -g jtraigle | sed 's/ /,/g')
/usr/sam/lbin/usermod.sam -F -G ${CUR_GROUPS},4000

[unixnewbie]

Thanks Mel and Jeff for the scripts.
I was under the assumption that usermod -G or usermod.sam -G will add the user to a secondary group keeping the current groups intact.

UVK, what Jeff told is right. It will replace the group list. Even usermod does so..
# usermod -G 4001 test

# id test
uid=101(test) gid=20(users) groups=4001(oper)

# usermod -G 4000 test

# id test
uid=101(test) gid=20(users) groups=4000(operm)