Linux Essentials

Why can a regular Linux user run the passwd command to change their own password, even though the binary is owned by root?

• Because all commands are allowed to all users by default

• Because /etc/shadow is world writable

• Because passwd is run as part of the kernel

• Because passwd has the SUID bit set, allowing it to run with the permissions of the file owner

Answer explanation

The correct answer is:

Because passwd has the SUID bit set, allowing it to run with the permissions of the file owner ✅

A regular user can run passwd to change their own password because the binary has the setuid bit set, so it executes with root privileges and can update /etc/shadow on their behalf — but only after checking they are allowed to.

You just logged into a Linux system and want to explore detailed documentation about the mkdir command beyond the basic man page. You prefer a format with hyperlinks to jump between related topics. Which command would you use to access this enhanced, hypertext-style documentation for mkdir?

(1 Point)

• man mkdir

• mkdir --help

• info mkdir

• less mkdir

Answer explanation

The correct answer is:

info mkdir ✅

The info system provides hypertext-style documentation with links to related topics, making it more detailed and navigable than man.

What effect does increasing the compression level have when using the zip command?

(1 Point)

• It decreases the file size but increases the time taken to compress and decompress.

• It increases the file size and decreases compression speed

• It decreases both file size and compression speed without any trade-offs.

• It has no effect on compression speed or file size.

Answer explanation

The correct answer is:

It decreases the file size but increases the time taken to compress and decompress. ✅

• Description: Higher compression levels apply more complex algorithms. This usually reduces file size, but at the cost of slower compression (and sometimes decompression). It’s a trade-off between speed and space.

Where can you typically find documentation for installed software packages on a Linux system?

(1 Point)

• /usr/local/bin

• /etc

• /usr/share/doc

• /var/log

Answer explanation

The correct answer is:

/usr/share/doc ✅

Description: Most Linux distributions install package documentation, examples, and licenses under /usr/share/doc, organized by package name. This is where you can browse README files, configuration notes, and other docs for installed software.

How would you represent the symbolic permission rwxrw-r-- in octal notation?

(1 Point)

• 764

• 754

• 774

• 744

Answer explanation

The correct answer is:

764 ✅

Description:
Symbolic permissions break down as follows:

• Owner (rwx) → 7 (read=4 + write=2 + execute=1)

• Group (rw-) → 6 (read=4 + write=2)

• Others (r--) → 4 (read=4)

So, rwxrw-r-- = 764.

In Linux, what primarily determines if a file can be executed, regardless of its extension?

(1 Point)

• The filename’s length

• The file’s extension, such as .sh or .bin

• The file’s execute permission and its content type

• The alphabetical order of the filename

Answer explanation

The correct answer is:

The file’s execute permission and its content type ✅

Description:
In Linux, a file is only runnable if it has the execute permission (x) set. The system also looks at the content type (like a shebang #!/bin/bash for scripts, or ELF headers for binaries) to know how to run it. File extensions don’t matter.

Which of the following best describes the Ubuntu release model for Long Term Support versions?

(1 Point)

• Release only when critical security issues arise

• Release every 6 months with 9 months support

• Scheduled release every 2 years with 5 years support

• Release randomly as per development progress

Answer explanation

The correct answer is:

Scheduled release every 2 years with 5 years support ✅

Description:
Ubuntu’s Long Term Support (LTS) versions are released on a fixed 2-year cycle (April of even-numbered years) and receive 5 years of official security updates and maintenance, making them stable for production and enterprise use.

Which of the following is an example of an absolute path in Linux?

(1 Point)

• Documents/Reports/file.txt

• /home/user/Documents/file.txt

• ../Pictures/image.png

• Downloads/music.mp3

Answer explanation

The correct answer is:

/home/user/Documents/file.txt ✅

Description:
An absolute path starts from the root directory (/) and specifies the full location of a file or directory. Relative paths (like Documents/..., ../Pictures/..., Downloads/...) depend on your current working directory.

How would you change the group ownership of a file named file1 to a group named developers?

(1 Point)

• chown developers file1

• chgrp developers file1

• chmod developers file1

• chown :developers file1

Answer explanation

The correct answer is:

chgrp developers file1 ✅

Description:
The chgrp command changes the group ownership of a file. Alternatively, you can use chown :developers file1, which also changes the group while keeping the owner unchanged.

If you create three users sequentially on a fresh Linux installation, what will be the most likely UID assigned to the third user?

(1 Point)

• 1000

• 1002

• 501

• 3

Answer explanation

The correct answer is:

1002 ✅

Description:
On most modern Linux distributions, user IDs (UIDs) for regular users start at 1000.

• First user → UID 1000

• Second user → UID 1001

• Third user → UID 1002

System users typically have UIDs below 1000.