010-160 System Security & User Permissions 3

Question 1

Which file defines which users and groups can use sudo?

Accepted Answer

/etc/sudoers

Answer

/etc/sudoers (edited safely with visudo) controls sudo access policies.

Question 2

How would you add an existing user 'alice' to the 'wheel' group without removing her from other groups?

Accepted Answer

usermod -aG wheel alice

Answer

`usermod -aG wheel alice` appends (-a) alice to the supplementary group (-G) wheel.

Question 3

What does 'umask 027' mean for newly created files?

Accepted Answer

Files get permissions 640

Answer

Default file permissions (666) minus umask (027) = 640, giving rw-r----- for new files.

Question 4

Which command locks a user account so they cannot log in with a password?

Accepted Answer

usermod -L username

Answer

`usermod -L username` locks the account by prepending a '!' to the password hash in /etc/shadow.

Question 5

In the output of `ls -l`, what does the first character 'd' indicate?

Accepted Answer

The item is a directory

Answer

A 'd' as the first character of the permission string indicates the item is a directory.

(010-160) LPI Linux Essentials Practice Test