Linux User Management

useradd manual

userdel manual

usermod manual

passwd manual

groupadd manual

groupdel manual

groups manual

sudo manual

su manual

List all users cat /etc/passwd It’s the first column. Or awk -F : ‘{print $1, “uid=”$3, “gid=”$3}’ /etc/passwd

List the default settings for adding a new user useradd -D The shell will often be just /bin/sh, which is not what you want

Add a new user sudo useradd -c “Joe Bloggs” -m -s “/bin/bash” jbloggs then sudo passwd jbloggs to set his password. If you set it to something simple, then use sudo passwd -e USER they will have to change their password on first login.

Login as another user su jbloggs

Delete a user, including their home directory sudo userdel -r USER. The command deluser can remove all files owned by the user as well.

Lock and unlock an account sudo usermod -L USER and sudo usermod -U USER

Set an account to expire on a date sudo usermod -e 2018-08-14

Create and delete groups sudo groupadd GROUP and sudo groupdel GROUP

Add a user into some more groups sudo usermod -a -G ADDITIONALGROUPs USER

Specify exactly the groups a user is a member of sudo usermod -G GROUP1,GROUP2,GROUPN USER. If the user is a member of a group not specified then they will be removed from that group.

Remove a user from a group sudo deluser USER GROUP

Enable a user to do sudo usermod -a -G sudo USER

List groups a user is a member of groups USER or just groups for your own account. To see the numerical Ids as well, do id USER.