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User and Group Management

Creating and Managing Users and Groups

1. Creating Users:

   • useradd: Command to create a new user.

     useradd username      # Creates a new user without a home directory
     useradd -m username   # Creates a new user with a home directory at /home/username
     

   • Options:

     • -m: Creates the user’s home directory if it does not exist.
     • -s /bin/bash: Specifies the default shell for the user.
     • -c "User Name": Adds a comment (usually the full name of the user).

2. Setting Passwords:

   • passwd: Command to set or change a user’s password.

     passwd username       # Prompts to set a new password for the user
     passwd                # Changes the password of the current user if run without a username
     

3. Creating Groups:

   • groupadd: Command to create a new group.

     groupadd groupname    # Creates a new group
     

   • Options:

     • -g GID: Specifies the group ID for the new group.

4. Modifying Users and Groups:

   • usermod: Command to modify user attributes.

     usermod -aG groupname username   # Adds the user to an additional group
     usermod -l newname oldname       # Changes the username
     

   • Options:

     • -aG: Adds the user to the specified group(s) without removing them from other groups.
     • -l: Changes the user’s login name.

   • groupmod: Command to modify group attributes.

     groupmod -n newgroup oldgroup    # Changes the group name
     

5. Deleting Users and Groups:

   • userdel: Command to delete a user.

     userdel username       # Deletes the user account
     userdel -r username    # Deletes the user account and the home directory
     

   • groupdel: Command to delete a group.

     groupdel groupname     # Deletes the group
     

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