Users

Command	Description
adduser	add a user to the system
usermod	modify a user account
userdel	delete a user account and related files
chage	change user password expiry information
sudo	run one or more commands as another user
id	find out user and group names and numeric ID’s (UID or group ID) of the current user or any other user in the server. ID 0 is preserved for the superuser root.user ID’s ranged from 1 to 99 are preserved for system users.user ID’s ranged from 100 to 999 are preserved for special use, but generally they are also used for system users.user ID’s ranged from 1000 and up are preserved for ordinary users like eva, junior etc.

Add new user

$ sudo adduser eva
$ sudo useradd -c "Description" -m -g group -n adam
$ sudo passwd eva

Disable user

$ sudo passwd -l 'eva'

Delete user

$ sudo userdel -r 'eva'

Lock/unlock student

$ sudo usermod --lock eva
$ sudo usermod --unlock eva

Set the expiration date

$ sudo usermod --expire-date 2020-01-14 eva

Force user to change his password

$ sudo chage --maxdays 60 eva

Groups

Command	Description
groupadd	Adds a new group.
groupmod	Modifies an existing group’s attributes.
groupdel	Deletes an existing group.

The information for groups is stored in /etc/group

$ tail -2 /etc/group
$ grep workers /etc/group

Create new group

$ addgroup workers

Check that a new group was added

$ getent group workers

Change the group name

$ groupmod -n workers new_workers

Change group ID

$ groupmod -g 7000 workers

Remove group

$ delgroup workers

Add existing user to a group

$ usermod -a -G workers eva

Remove user from the group

$ deluser eva workers

Change user primary group

$ usermod -g new_group eva