user, group, passwd - alex-aleyan/linux_wiki GitHub Wiki

1. Useful Administrative Files:

   /etc/group            - Group account information.
   /etc/passwd           - user account information
   /etc/shadow           - secure user account information
   /etc/gshadow          - shadow secure user account information
   
   /etc/login.defs       - Shadow password suite configuration.
   /etc/default/useradd  - Default values for account creation.
   /etc/skel/            - Directory containing default files.
   /etc/pam.d/passwd     - PAM configuration for passwd.
   

2. Useful Administrative Commands:

   useradd, adduser      - create a user
   groupadd              - create a user
   lslogins              - Lists user's info including the DEFAULT SHELL.
   chsh                  - Allows the user to change the user's login shell.
   usermod,passwd        - used to change user's account settings (authentication expiration, lock/unlock account).
   chfn                  - used to change a user's finger information (full name, office, office-phone, home-phone)
   

userdel -r username 

1. Create a user:

   [root@test1 ~]# useradd user1
   [root@test1 ~]# echo $USER
   [root@test1 ~]# echo $USERNAME 
   

2. Verify the user was created:

   [root@test1 ~]# cat /etc/passwd | grep user1
   user1:x:500:100::/home/user1:/bin/bash
   

3. Create a group:

   [root@test1 ~]# groupadd users
   

4. Verify that the group was created:

   [root@test1 ~]# cat /etc/group | grep users
   users:x:100:
   

5. Add the user to the group:

   [root@test1 ~]# gpasswd -a <username> <groupname>
   [root@test1 ~]# gpasswd -a user1 users
   

6. To set/cahnge password:

   [root@test1 ~]$ passwd
   [root@test1 ~]# passwd userName
   

7. To delete a user from a group:

   [root@test1 ~]# gpasswd -d <username> <groupname>
   

8. Hint: you can also use this command to list basic info of a user. Use ''lslogins'' by itself to list the summary about all accounts on a system.:

   lslogins userName
   OR
   lslogins id
   

9. Edit Primary group of a user:

   usermod userName -g groupName
   

Quick Review:

chage -l <username>
passwd -x -1 <username>
chage -m 0 <username>

On host1:

1. Skip to Step 5; Remove user:

   userdel myuser
   

2. Remove user’s home directory:

   rm –fr /home/myuser
   

3. Add user:

   useradd user1
   

4. Add the user to a group

   gpasswd -a myuser -g users
   

5. List users to determine the UUID of the user:

   lslogins #to see UUID of myuser
   

On host2:

1. SSH as root.

2. Using the UUID from host1, change the UUID of myuser on host2 to match the UUID found on host1:

   usermod -u <matchin UUID> myuser

On all hosts do:

1. Make sure the next parameters are set as:

   chage -l myuser
   Last password change					: Dec 22, 2016
   Password expires					: never
   Password inactive					: never
   Account expires						: never
   Minimum number of days between password change		: -1
   Maximum number of days between password change		: -1
   Number of days of warning before password expires	: -1
   

2. if not, set them using:

   chage -E -1 –I -1 –m -1 –M -1 –W -1 myuser

1. Uncomment the "%wheel ALL=(ALL) ALL" line:

   [root@test1 ~]# visudo
   ## Allows people in group wheel to run all commands
   # %wheel        ALL=(ALL)       ALL
   

2. Optionally, add command path so the sudoers can launch the commands in the path:

   Defaults secure_path = /sbin:/bin:/<yourpathhere>

3. List the users:

   [root@test1 ~]# cat /etc/passwd

4. Add a user to sudoers group (wheel group is a group with god previleges):

   [root@test1 ~]# usermod -aG wheel <USERNAME>

5. Test the sudoer:

   [root@test1 ~]# su <USERNAME>
   [user@test1 ~]$ groups #make sure user is in the wheel group
   [user@test1 ~]$ sudo whoami
   

6. To remove a user from a group:

   gpasswd -d userName groupName

1. Check if there are any failed logins. The below command will show how many failed logins the particular username has.

   #pam_tally --user <username>

2. Unlock the user/Reset the failed logins

   #pam_tally --user <username> --reset

   • For all users, you can simply give

     #pam_tally --reset