Cheatsheet

command meaning
whoami show which user is logged in
passwd change password of current user
passwd jane change Jane’s password
su become superuser / change user to root
su jane change user to jane
sudo superuser do = do it as a superuser
adduser james add a user named ‘james’
deluser james delete the user ‘james’
passwd -l jane lock jane’s password
passwd –lock jane lock jane’s password

whoami

shows which user is logged in

passwd

change the password for the current user. passwd jane = Change Jane’s password

su

SuperUser. login to a different user, for example su jalal = login to jalal’s account. only su without a username provided will change to root user by default.

su root

login to a different user, in this case root. su and su root will both do the same thing.

adduser

add a user. for example, adduser jane will add a user called jane. You need root/sudo access/permissions to cerate or delete a user.

userdel

delete a user. for example: userdel jalal will delete the user named jalal. Use the -r flag to delete the user BUT keep the user’s directory/files. For example: userdel -r jalal will delete a user named jalal but keep his home directory and other files.

Locking a user’s password -l or --lock

passwd -l jane

The passwd command with the -l or --lock flag will lock the password of the named account (in our example, jane). Users with a locked password are not allowed to change their password.

Note that this does not disable the account. You need to be root (or have sudo priveleges) to be able to lock a user’s password.

Adding trusted sudo users

Sudo allows regular users to run commands as a super user. That way you won’t have to be running as root the whole time.

If you are on Ubuntu, sudo is already installed for you. If you are on Debian, you’ll have to install sudo:

apt-get install sudo

If the package is not found then you’ll have to update the system.

apt-get update

The above command will update our linux machine with all of the available source for apt-get.

Now that you have sudo installed, you’ll need to create/edit the sudoers file. This file is located in the /etc directory.

cd /etc
nano sudoers

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