Linux - Basic User Management
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
Super User. 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
whoami = check which user are you
su = switch to Super User
passwd = change password
Change password
passwd
will prompt to change the password for the current user
passwd john
will prompt to chnage the password for user ‘john’.
Add User
useradd james
will add a user called ‘james’. Adding user requires sudo priveleges.
Remove a user
You have a couple of options:
- change his password
- lock the user
delete him from the system
userdel -r john
Check if a user has been added
The -r flag removes the home directory of the particular user from the system. You can not delete a user that’s logged in.
You can check if a user is part of the system by checking the password file.
cat /etc/passwd
In some cases, the act of creating a user does not create the directory, only when that user logs in the first time will the home directory be created. You can check if your user was created by doing a:
sudo cat /etc/passwd | grep USERNAME
Creating user directory
Ubuntu considers the useradd utility a low level utility and sets it so that the homedir is not added by default. You fan manually add the directory if the user is created.
useradd -m USERNAME
In Ubuntu, adduser creates a directory for new users by default. If not, you can use the -d flag.
If you want to specify the path of the home directory, use:
useradd -m d /PATH/TO/FOLDER USERNAME