Users and groups

Question 1

Add user in Linux?

Answer 1

“useradd” is the command

Question 2

Can we modify user?

Answer 2

Yes, “usermod” is the command

Question 3

Default values for users

Answer 3

/etc/login/defs
/etc/skel
/etc/default/useradd

Question 4

What is the easiest way to access super user privileges?

Answer 4

su (substitute user) is the command
login as other user: su -
login as root: su -

Question 5

Add password for user

Answer 5

passwd is the command

Question 6

When do we need super user privileges?

Answer 6

System wide changes
Changes that affect other user
Configure services

Question 7

View and set password policies (expiry date, etc..)

Answer 7

chage is the command
chage -l lists user password policy
note: policies include expiry period, etc.

Question 8

How to create a group on Linux?

Answer 8

groupadd is the command

Question 9

Modify and add users to groups on Linux?

Answer 9

groupmod to modify
gpasswd to add user
we can also add users to a group on useradd/usermod commands

Question 10

View groups and users?

Answer 10

List users: /etc/passwd file
List user passwords: /etc/shadow file
List groups: /etc/group file
We can also use getent command - getnet passwd , getent group
We can use groups command as well to list user in a group - groups

Question 11

What if I just want to perform a single command with supper user privileges?

Answer 11

We can use “sudo” command

Question 12

Who is allowed to use “sudo” command?

Answer 12

Groups authorized in /etc/sudoers file
Groups like “sudo”, etc..
We can also authorize certain groups to execute certain commands on certain machines

Question 13

How to edit sudoers file?

Answer 13

Best to use “visudo” command

Note: we need super user privileges

Question 14

How to change password lenght and complexity policies in Linux?

Answer 14

Modify /etc/security/pwquality.conf