Education Part 02 – CentOS 7 Users & Groups

A big part of Linux is managing users and groups.  Eventually I will setup and configure LDAP, but until then I am just doing this on the local machine.

I made myself root so that I did not have to constantly type sudo.

#  su -

Create three users in CentOS:

# useradd david
# useradd christine
# useradd ccf

Create a user that is not permitted to log in to the system.  (Like when setting up Samba).

# useradd -s /usr/sbin/nologin no_login_test

Set passwords for the users:

# passwd david
# passwd ccf
# passwd christine

Set an expiration date for a user:

# usermod --expiredate=2015-03-29 ccf

Verify the expiration date:

# chage -l ccf

 Creating Groups:

# groupadd test1
# groupadd test2
# groupadd developers

Add a user to a group or groups:

# usermod -G developers -a david
# usermod -G test1 - a david

Verify which groups the user is now in:

# groups david
david : david test 1 developers

Lock a user account (stops them from being able to login):

# usermod -L ccf

Unlock a user account (permits them to log back into the system):

# usermod -U ccf

Deleting a group:

# groupdel test2

Deleting a user – the -r switch deletes all traces of the user including their home directory.

# userdel -r ccf

Give a user root access

# gpasswd -a david wheel

This adds the user to the wheel group, and gives them sudo access to the system.  I suppose no more visudo?

Log In as that user and test it out:

# sudo -l david
# sudo yum search chrome

Change a users home directory.

Create/locate the directory you want to use for my experiment I created a new directory:

# mkdir /mnt/fake_home
# usermod -d /mnt/fake_home christine

Verify that it worked:

# grep -E --color '/mnt/fake_home' /etc/passwd
christine:x:1002:1002::/mnt/fake_home:/bin/bash

Changing a user’s primary group.

First verify the users current group

# id christine
uid=1002(christine) gid=1002(christine) groups=1002(christine),1006(developer)

Now we will set the primary group to test1

# usermod -g test1 christine

Verify the change

# id christine
# uid=1002(christine) gid=1002(christine) groups=1004(test1),1006(developer)

Set an un-encrypted password for a user

# usermod -p password plinko

View the password:

# cat /etc/shadow | grep plinko
plinko:password:16522:0:99999:7:::

QUESTION:  Why would anyone want to create an account with an unencrypted password?