Adding, Deleting, and Modifying User Groups

Question 1

What is our go-to command for manipulating users?

Answer 1

useradd

Question 2

What does the useradd command do?

Answer 2

It adds a new user.

Question 3

What is the synopsis of the useradd command when we man it?

Answer 3

useradd [OPTIONS] LOGIN

Question 4

What do we need in order to add a user using the useradd command?

Answer 4

We need to have administrator rights.

Question 5

What is the most basic real-world example of using the useradd command, and what do we get asked for when we execute it?

Answer 5

1. sudo useradd jdoe

2. Our password.

Question 6

What flag do we use with useradd to specify a comment?

Answer 6

The -c flag.

Question 7

What do most distros store in the comment for a given user?

Answer 7

The full name of the user.

Question 8

What is the most basic real-world example of creating a user and give them a comment using the useradd command?

Answer 8

sudo useradd -c "Jane Smith" jsmith

Question 9

How do you set an expiration date for a user when creating it with the useradd command?

Answer 9

By using the -e flag.

eg.
~~~
sudo useradd -e 2019/12/31 jsmith
~~~

Question 10

What is the format accepted by the -e flag when using the useradd command?

Answer 10

YYYY/MM/DD

eg. 2019/12/31

Question 11

How do you set the default shell for a user when creating it with the useradd command?

Answer 11

By using the -s flag and giving it the path to the binary for that particular shell.

eg.
~~~
sudo useradd -s /bin/zsh jsmith
~~~

Question 12

What is the path to the default home directory for a given user?

Answer 12

/home/[username]

eg.
If the username is “jsmith”, the home directory would be home/jsmith.

Question 13

How do we specify a non-default home directory for a given user when creating it using the useradd command?

Answer 13

By using the -d flag.

eg.
~~~
sudo useradd -d /home/johnsmith jsmith
~~~

Question 14

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?

Answer 14

1. We must create the folder that we specified as the user’s home directory.
2. Because unlike using the default home directory, when we specify a custom home directory for a user when creating one with the useradd command, the home directory we specified will not be created.

Question 15

How do you print the ID of a user on the terminal?

Answer 15

By using the id command and giving it the username that we want to get the ID for.

eg.
~~~
sudo id sarah
~~~

Question 16

How do you delete a user using the terminal?

Answer 16

By using the userdel command and giving it the username of the user we’d like to delete.

eg.
~~~
sudo userdel sarah
~~~

Question 17

How do you specify that the home directory of the given user should be deleted when using the userdel command?

Answer 17

By using the -r flag.

eg.
~~~
sudo userdel -r sarah
~~~

Question 18

What does the usermod command do?

Answer 18

It modifies a user account.

Question 19

How do you modify a user account?

Answer 19

By using the usermod command.

eg.
~~~
sudo usermod -c “Not Sarah” sarah
~~~

Question 20

How do you change the username of an account using the usermod command?

Answer 20

By using the -l flag.

eg.

sudo usermod -l sjones sarah
~~~
…will change the username from sarah to sjones.
~~~

Question 21

What is the default password for users that are added using the useradd command, and what does this mean?

Answer 21

1. Nothing. There is no default password for the users created by the useradd command.
2. User accounts without passwords will NOT function. They simply won’t work until we attach a password to them.

Question 22

How can you attach a password to a user that was created by the useradd command?

Answer 22

By using the passwd command.

eg.

sudo passwd sjones
~~~
…will prompt us for a new password for the user sjones
~~~

Question 23

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.

Answer 23

By using the chage command.

Question 24

What does the chage command do?

Answer 24

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.

Question 25

How do you display information about the password changes of a user?

Answer 25

By using the chage command and the -l flag.

eg.
~~~
sudo chage -l sjones
~~~

Question 26

How do you browse the default values that are used by the useradd command when adding a new user?

Answer 26

By using the -D command.

eg.
~~~
sudo useradd -D
~~~

Question 27

What is a skeleton directory?

Answer 27

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.

Question 28

How do you explicitly specify a home directory to be created for the new user when using the useradd command?

Answer 28

By using the -m flag.

eg.
~~~
sudo useradd sjones -m
~~~

Question 29

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?

Answer 29

1. By using the -k flag.

eg.
~~~
sudo useradd sjones -k /etc/skel
~~~

2. 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 -m flag.

eg.
~~~
sudo useradd sjones -k /etc/skel -m
~~~