Linux user management commands

Create user in linux :

root@test2:~# useradd test1
root@test2:~# passwd test1
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully

Note : we can also create user with adduser command.

-Whenever user is created in linux the default access is assigned to user via /etc/profile file.
-Username is added to /etc/passwd file.
-Same as username one group is created in /etc/group file.
-Encrypted password save into /etc/shadow file.


Delete user in linux:

root@test2:~# userdel test1

Lock user account in linux:

root@test2:~# passwd -l test1
passwd: password expiry information changed.

when user will try to login he will get below message.

login as: test1

test1@192.168.0.10's password:

Access denied

When the user account is locked we can see ! sign after username in /etc/shadow file.

root@test2:~# cat /etc/shadow | grep test

test1:!$6$prWdpshs$A0WNBzbHC5sEke7hatNq8lFaB/Ux.SQ3vRc1.If4joDTD/AMpsuPYT.1mCmfBDUCoh6ND7izfcT9buo1wiZ581:17066:0:99999:7:::

Unlock user account in linux:

root@test2:~# passwd -u test1

passwd: password expiry information changed.

You can also unlock by editing /etc/sadow file. remove the ! sign from locked account.

Linux user account details :

root@test2:~# chage -l test1

Last password change                                    : Sep 22, 2016

Password expires                                        : never

Password inactive                                       : never

Account expires                                         : never

Minimum number of days between password change          : 0

Maximum number of days between password change          : 99999

Number of days of warning before password expires       : 7

See process run by user :

root@test2:~# ps  -u test1

  PID TTY          TIME CMD

 2442 ?        00:00:00 systemd

 2443 ?        00:00:00 (sd-pam)

 2463 ?        00:00:00 sshd

 2464 pts/0    00:00:00 sh

Root access to test1 user :

Edit the /etc/sudoers and add the below line.

%test1  ALL=(ALL:ALL) ALL

Switch to another user :

sudo su - username

root@test2:~# sudo su - test1

No directory, logging in with HOME=/

$ bash

test1@test2:/$