groups <username> # to check groups of a user
usermod -G <groupname> <username> # to add a user to a group
usermod -G <groupname> -d <directory> <username> # to change the home directory of a user
usermod -s <shell> <username> # to change the shell of a user

# give user sudo access
sudo vim /etc/sudoers
<username> ALL=(ALL) ALL # add the line above to the end of the file

# add user to sudo|wheel group
sudo usermod -aG sudo <username>

su

Switch shell to another user.
More information: https://manned.org/su.

 - Switch to superuser (requires the root password):
   su

 - Switch to a given user (requires the user's password):
   su username

 - Switch to a given user and simulate a full login shell:
   su - username

 - Execute a command as another user:
   su - username -c "command"

adduser

User addition utility.
More information: https://manned.org/adduser.

 - Create a new user with a default home directory and prompt the user to set a password:
   adduser username

 - Create a new user without a home directory:
   adduser --no-create-home username

 - Create a new user with a home directory at the specified path:
   adduser --home path/to/home username

 - Create a new user with the specified shell set as the login shell:
   adduser --shell path/to/shell username

 - Create a new user belonging to the specified group:
   adduser --ingroup group username

users

Display a list of logged in users.
See also: useradd, userdel, usermod.
More information: https://www.gnu.org/software/coreutils/users.

 - Print logged in usernames:
   users

 - Print logged in usernames according to a given file:
   users /var/log/wmtp

usermod

Modify a user account.
See also: users, useradd, userdel.
More information: https://manned.org/usermod.

 - Change a username:
   sudo usermod -l|--login new_username username

 - Change a user ID:
   sudo usermod -u|--uid id username

 - Change a user shell:
   sudo usermod -s|--shell path/to/shell username

 - Add a user to supplementary groups (mind the lack of whitespace):
   sudo usermod -a|--append -G|--groups group1,group2,... username

 - Change a user home directory:
   sudo usermod -m|--move-home -d|--home path/to/new_home username

gpasswd

Administer /etc/group and /etc/gshadow.
More information: https://manned.org/gpasswd.

 - Define group administrators:
   sudo gpasswd -A user1,user2 group

 - Set the list of group members:
   sudo gpasswd -M user1,user2 group

 - Create a password for the named group:
   gpasswd group

 - Add a user to the named group:
   gpasswd -a user group

 - Remove a user from the named group:
   gpasswd -d user group

(base) ➜  ~ gpasswd
Usage: gpasswd [option] GROUP

Options:
  -a, --add USER                add USER to GROUP
  -d, --delete USER             remove USER from GROUP
  -h, --help                    display this help message and exit
  -Q, --root CHROOT_DIR         directory to chroot into
  -r, --remove-password         remove the GROUP's password
  -R, --restrict                restrict access to GROUP to its members
  -M, --members USER,...        set the list of members of GROUP
  -A, --administrators ADMIN,...
                                set the list of administrators for GROUP
Except for the -A and -M options, the options cannot be combined.

delete user

In Debian 12, the deluser and userdel commands are used to delete users. However, if you can't find these commands, it might be due to a missing package or a typo. Here's how you can delete a user in Debian 12:

1. Using deluser (Recommended)

The deluser command is part of the passwd package and is the preferred method for removing users in Debian.

Steps:

1. Install the passwd package (if not already installed):

   sudo apt update
   sudo apt install passwd
   

2. Delete the user:

   sudo deluser username
   

   Replace username with the actual username you want to delete.

3. Delete the user's home directory and mail spool (optional):

   sudo deluser --remove-home username
   

2. Using userdel

The userdel command is part of the shadow-utils package and is a lower-level tool for removing users.

Steps:

1. Install the shadow-utils package (if not already installed):

   sudo apt update
   sudo apt install shadow-utils
   

2. Delete the user:

   sudo userdel username
   

3. Delete the user's home directory and mail spool (optional):

   sudo rm -rf /home/username
   sudo rm -rf /var/mail/username
   

Troubleshooting

• Command not found: If you get a "command not found" error, ensure that the passwd or shadow-utils package is installed.
• Typo: Double-check the spelling of the commands (deluser and userdel).

Summary

• Use deluser for a more user-friendly experience.
• Use userdel for a more manual approach.
• Always ensure the necessary packages are installed.

Let me know if you encounter any issues!