Managing users & Groups

Question 1

What command do we use to create a user account?

Answer 1

useradd

• c Full Name
• e Expiration date
• s Default shell
• d Home directory

useradd jdoe -c “John Doe” -e 2019/12/31 -s /bin/dash -d /home/john_doe

Question 2

What is userdel command in Linux?

Answer 2

Stands for: User delete

Function: Delete a user account and related files

Question 3

What command and option is for completely deleting a user?

Answer 3

userdel -r

Question 4

What command modifies a user account?

Answer 4

usermod

• Rename account: usermod -l jdoe jsmith
• Lock account: usermod -L jdoe
• Unlock account: usermod -U jdoe
• Add user to group: usermod -a -G Marketing

Question 5

What command changes the login shell of username?

Answer 5

chsh

• Prevent an account from logging in interactively
• e.g. chsh -s /bin/nologin

Question 6

What is the command to set or change a user password?

Answer 6

passwd

Question 7

How do you set an expiration for a user account password?

Answer 7

*chage

Define password expiration policy

Question 8

How do you display current password info for a user?

Answer 8

*Display current info

chage -l jdoe

Question 9

How do you modify a password policy for a user?

Answer 9

*Modify policy

chage -m -M -E -W jdoe

Question 10

How do you display defaults of a user account?

Answer 10

useradd -D (displays defaults)

List of defaults
/etc/login.defs
/etc/default/useradd
/etc/skel

Question 11

How can we verify a user account’s configuration?

Answer 11

*/etc/passwd (account info)
Defines accounts
User ID
UIDs typically start at 500
Users/Groups can share an ID (not ideal)
*/etc/shadow (password file)
*/etc/group (group association)

Question 12

What command do we use to create groups?

Answer 12

*groupadd
groupadd Marketing

*/etc/group
list of groups

Question 13

Are we able to modify the group once it is created?

Answer 13

YES

*groupdel (deletes group)

*groupmod (modifies)
(-n Rename group)
groupmod -n

Question 14

How do we put user accounts into the groups?

Answer 14

gpasswd

*Add a user
gpasswd -a

*Remove a user
gpasswd -d

*Add a group admin
gpasswd -A

Question 15

Are secondary group permissions applied automatically?

Answer 15

NO

Users perform all actions under their primary group by default

Question 16

What does the newgrp command do?

Answer 16

The newgrp command is used to change the current group ID during a login session.

Question 17

What does the chgrp command do?

Answer 17

The chgrp (change group) command alters the group name that a file or directory belongs to.

Question 18

What does the groups command do?

Answer 18

The groups command lists the groups that a user belongs to.

groups

Question 19

Are there any other ways to verify a group’s configuration?

Answer 19

getent passwd (looks into etc/passwd and looks for user info)

getent shadow (looks into etc/passwd and looks for user password)

getent group  (looks into etc/passwd and looks for user group)
groups  (lists all groups that user is part of)