Linux – /are the standard CLI program(s) to manage users and groups

linuxusersUtilities

I'm basically asking about user management from the command line (e.g. on a system where there are no graphical tools available). In the past I've used several different programs to add or delete users and groups or to modify their attributes: adduser, useradd, usermod, gpasswd, and perhaps others I've forgotten. I've also heard a couple times that some of these programs are low-level and should be avoided for general use, but I can never remember which. So I'd like to get a definitive answer for which programs are the recommended ones for at least the following tasks:

Create a new user
Add a user to a group
Remove a user from a group
Change a user's primary group
Change a user's login shell or home directory
Delete a user

I'm looking for standard tools which I can expect to be available on pretty much any Linux system (of any distribution).

Best Answer

Sadly, none of those operations were ever standardized.

Some operating systems offer this functionality as part of the OS, like Linux, but even if your Linux system includes them, over time and across Linux distributions the tools and their names changed so you can not really depend on a standard set of tools to do those tasks.

You need to have a per-operating system set of tools.

Related Solutions

Linux – How to Change a User’s Default Group

The usermod command will allow you to change a user's primary group, supplementary group or a number of other attributes. The -g switch controls the primary group.

For your other questions...

If you specify a group, groupname, that does not exist during the useradd stage, you will receive an error - useradd: unknown group groupname
The groupadd command creates new groups.
The group will remain if you remove all users contained within. You don't necessarily have to remove the empty group.
Create the hilbert group via groupadd hilbert. Then move David's primary group using usermod -g hilbert hilbert. (Please note that the first hilbert is the group name and the second hilbert is the username. This is important in cases, where you are moving a user to a group with a different name)

You may be complicating things a bit here, though. In many Linux distributions, a simple useradd hilbert will create the user hilbert and a group of the same name as the primary. I would add supplementary groups specified together using the -G switch.

User created without a password behaves as if he had one

A user is created by default as a locked account. The field that should contain the password hash in /etc/shadow will contain !!. When an account is locked, that account is available to root only (root can su but logins aren't allowed). If you 'unlock' the account which simply removes the !! you will be allowed to change the password.

[root@test ~]# su - test
[test@test ~]$ passwd
Changing password for user test.
Changing password for test.
(current) UNIX password:
[test@test ~]$ exit
logout
[root@test ~]# passwd -u test
Unlocking password for user test.
passwd: Warning: unlocked password would be empty.
passwd: Unsafe operation (use -f to force)
[root@test ~]# passwd -u test -f
Unlocking password for user test.
passwd: Success
[root@test ~]# su - test
[test@test ~]$ passwd
Changing password for user test.
New password:

Best Answer

Related Solutions

Linux – How to Change a User’s Default Group

User created without a password behaves as if he had one

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