Linux commands for working with users and groups in the terminal.

Linux-Terminal-Users-CRUD.md

Important Files and Paths

• /etc/login.defs is the configuration file for login parameters, containing some defaults that are used for the commands below.
• /etc/adduser.conf contains the default configuration and settings for creating new users with adduser
• The default files for new users is stored in /etc/skel, though this can be changed in /etc/adduser.conf
• The user database is stored at /etc/passwd
• User passwords are stored in /etc/shadow
• Group info is stored at /etc/group

Find all users that login through the terminal.

sudo awk -F':' '$2 ~ "\\$" {print $1}' /etc/shadow

Get the groups a user belongs to.

groups username

Get the GIDs a user belongs to.

id username id uid

Add a group

addgroup

Add a user

• Omitting the groupname argument will cause a new group to be created with the same name as the new user.

adduser username groupname

Delete a user

deluser

Change a users password

passwd

Change group passwords

gpasswd

Modify a user

• Where adduser only allows the user to be added to one group, usermod allows a user to be added to multiple groups. usermod chfn

Give password an expiration date

chage

Set a disk usage quota

edquota

Regarding Sudo

To grant sudo privileges to an existing user, usermod -aG sudo username

Miscellaneous

To switch users without having to logout and back in, su - username

For more information:

• https://www.computerhope.com/unix/adduser.htm
• https://linux.die.net/man/8/adduser
• http://linuxadministrative.blogspot.com/2014/05/adduser-command-examples.html
• https://www.linuxtechi.com/linux-commands-to-manage-local-accounts/