Adding, Deleting, and Modifying User Groups Flashcards
What is our go-to command for manipulating users?
useradd
What does the useradd command do?
It adds a new user.
What is the synopsis of the useradd command when we man it?
useradd [OPTIONS] LOGIN
What do we need in order to add a user using the useradd command?
We need to have administrator rights.
What is the most basic real-world example of using the useradd command, and what do we get asked for when we execute it?
sudo useradd jdoe
2. Our password.
What flag do we use with useradd to specify a comment?
The -c flag.
What do most distros store in the comment for a given user?
The full name of the user.
What is the most basic real-world example of creating a user and give them a comment using the useradd command?
sudo useradd -c "Jane Smith" jsmith
How do you set an expiration date for a user when creating it with the useradd command?
By using the -e flag.
eg.
~~~
sudo useradd -e 2019/12/31 jsmith
~~~
What is the format accepted by the -e flag when using the useradd command?
YYYY/MM/DD
eg. 2019/12/31
How do you set the default shell for a user when creating it with the useradd command?
By using the -s flag and giving it the path to the binary for that particular shell.
eg.
~~~
sudo useradd -s /bin/zsh jsmith
~~~
What is the path to the default home directory for a given user?
/home/[username]
eg.
If the username is “jsmith”, the home directory would be home/jsmith.
How do we specify a non-default home directory for a given user when creating it using the useradd command?
By using the -d flag.
eg.
~~~
sudo useradd -d /home/johnsmith jsmith
~~~
When we’re using the useradd command to create a new user with a non-default home directory, what is the secondary step that we must undertake and why?
- We must create the folder that we specified as the user’s home directory.
- Because unlike using the default home directory, when we specify a custom home directory for a user when creating one with the
useraddcommand, the home directory we specified will not be created.
How do you print the ID of a user on the terminal?
By using the id command and giving it the username that we want to get the ID for.
eg.
~~~
sudo id sarah
~~~
How do you delete a user using the terminal?
By using the userdel command and giving it the username of the user we’d like to delete.
eg.
~~~
sudo userdel sarah
~~~
How do you specify that the home directory of the given user should be deleted when using the userdel command?
By using the -r flag.
eg.
~~~
sudo userdel -r sarah
~~~
What does the usermod command do?
It modifies a user account.
How do you modify a user account?
By using the usermod command.
eg.
~~~
sudo usermod -c “Not Sarah” sarah
~~~
How do you change the username of an account using the usermod command?
By using the -l flag.
eg.
sudo usermod -l sjones sarah
~~~
…will change the username from sarah to sjones.
~~~
What is the default password for users that are added using the useradd command, and what does this mean?
- Nothing. There is no default password for the users created by the
useraddcommand. - User accounts without passwords will NOT function. They simply won’t work until we attach a password to them.
How can you attach a password to a user that was created by the useradd command?
By using the passwd command.
eg.
sudo passwd sjones
~~~
…will prompt us for a new password for the user sjones
~~~
How do you set an expiration date for a user’s password?
eg. so that they have to change it before a certain date after they’ve started to use their account.
By using the chage command.
What does the chage command do?
It changes the number of days between password changes and the date of the last password change. This information is used by the system to determine whether a user must change his/her password.
How do you display information about the password changes of a user?
By using the chage command and the -l flag.
eg.
~~~
sudo chage -l sjones
~~~
How do you browse the default values that are used by the useradd command when adding a new user?
By using the -D command.
eg.
~~~
sudo useradd -D
~~~
What is a skeleton directory?
It is an important directory that is inside /etc. Whenever a new user is created, a new copy of the skeleton folder is created and put into the home directory of that new user.
How do you explicitly specify a home directory to be created for the new user when using the useradd command?
By using the -m flag.
eg.
~~~
sudo useradd sjones -m
~~~
How do you specify the skeleton directory when adding a new user using the useradd command, and what is the requirement to be able to do this?
- By using the
-kflag.
eg.
~~~
sudo useradd sjones -k /etc/skel
~~~
- The requirement is that we also need to create a new homefolder for the given user. This can be achieved in Ubuntu by using the
-mflag.
eg.
~~~
sudo useradd sjones -k /etc/skel -m
~~~
