useradd and multiple group question

bar338 · 11-23-2009, 10:06 AM

This is what i'm trying to do:
create a new user
add them to a primary group
add them to a couple secondary groups

The command i'm using right now

useradd -g developers <username>

this works but when i try to add secondary groups I get an error (I also want the users group to be a part of the secondary group.

useradd -g developers -G <username>,admins,wheel <username>

Does this make sense? and is it possible to do all this in one command? I'm currently able to do it but I have to perform a usermod command after I add the user. I think the real problem is adding the <username> group as a secondary group while the user is being created.

Thanks for your help.

EricTRA · 11-23-2009, 10:22 AM

Hello and welcome to LinuxQuestions,

The best info to start with is the man page for useradd:

Code:

man useradd

If you add a user with the useradd commando the you can specify a primary group with the -g and additional groups with the -G option:

Code:

-G group,[...]
              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  white-
              space.  The groups are subject to the same restrictions as the group given with the -g option.  The default is for the user to belong only to the
              initial group.

So if you want to add a user and set as primary group developers and as secondary group(s) print, sshd, etc...:

Code:

useradd username -g developers -G print,sshd,etc

Kind regards,

Eric

bar338 · 11-23-2009, 10:43 AM

Yes I understand this but I think I need to be more clear as to what my main question is.

Typically when you create a new user on my server and don't include any extra parameters it assigns the person to the <username> group. For example, if I add a user called jsmith his primary group will be jsmith.

Now I want to add a different primary group called developers for jsmith and add the group jsmith as a secondary group. I think the problem might be that when running a single command, which includes creating the user and assigning the 'jsmith' group as a secondary group, the secondary group can't be assigned because It hasn't been created yet at the point of the useradd command. Am I correct in understanding this? If so then I will have to use two commands to perform this action.

My exact command
sudo useradd jsmith -g developers -G jsmith,admins
Error message:
useradd: invalid numeric argument 'jsmith'

EricTRA · 11-23-2009, 11:05 AM

Hi,

The groups must exist before you can add users to them. When you don't assign a primary group then the useradd command creates a primary group with the same name as the username, like you said. If you want to add the user to additional groups these must exist.

So if you want for example to create a user, assign primary group users and additional groups developers,printer,etc...

If the groups developers and printers don't exist:

Code:

groupadd developers,printers
useradd username -g users -G developers,printers

If the groups already exist then of course you don't have to execute the groupadd command. As far as I know you cannot create a new user and assign him to a secondary group if that group has not been created. So yes, in my opinion you'll need two commands.

Kind regards,

Eric