Users and Groups

Question 1

Which of the following best describes the root account in Linux?

🔘 Options
A. A non-human background account used for services
B. A regular user account with limited access
C. The most powerful account with full system access
D. An account used only for SSH login

Answer 1

✅ Correct Answer
C. The most powerful account with full system access

💡 Explanation
A. ❌ This is a service account, not the root account.

B. ❌ A standard user, not root.

C. ✅ Correct — root can read, write, delete any file, and change system-wide settings.

D. ❌ Any user may be used for SSH — this isn’t exclusive to root.

Question 2

What is the purpose of the ‘sudoers’ file?

🔘 Options
A. To store service logs for user accounts
B. To define which users have administrative privileges
C. To manage login attempts and failures
D. To monitor background services

Answer 2

✅ Correct Answer
B. To define which users have administrative privileges

💡 Explanation
A. ❌ Service logs are handled by syslog, journald, etc.

B. ✅ Correct — the /etc/sudoers file controls sudo access.

C. ❌ That’s handled by log tools like faillog, not sudoers.

D. ❌ Background services are monitored by systemd or service tools.

Question 3

What makes visudo safer than editing /etc/sudoers directly?

🔘 Options
A. It opens in a hidden mode that can’t be seen by others
B. It encrypts the sudoers file
C. It checks for syntax errors and prevents lockout
D. It runs the file in a container

Answer 3

✅ Correct Answer
C. It checks for syntax errors and prevents lockout

💡 Explanation
A. ❌ Visudo isn’t hidden — it’s about safe editing.

B. ❌ No encryption is involved.

C. ✅ Correct — it checks syntax before saving to avoid locking you out of sudo.

D. ❌ There’s no container use — it’s just a safer editor wrapper.

Question 4

Which statement about sudoedit is true?

🔘 Options
A. It runs your editor as root, just like sudo nano
B. It lets you edit files with elevated privileges safely
C. It only works on .conf files
D. It replaces the sudoers file entirely

Answer 4

✅ Correct Answer
B. It lets you edit files with elevated privileges safely

💡 Explanation
A. ❌ sudoedit runs the editor as your user, not root.

B. ✅ Correct — it safely lets you edit, and uses sudo only to save changes.

C. ❌ It can edit any file, not just .conf.

D. ❌ It does not replace files, just edits them.

Question 5

What is the ‘wheel’ group used for in Linux?

🔘 Options
A. To restrict access to graphical applications
B. To limit SSH login attempts
C. To allow group members to use sudo
D. To monitor user activities

Answer 5

✅ Correct Answer
C. To allow group members to use sudo

💡 Explanation
A. ❌ Not related to GUI access.

B. ❌ SSH login policies are managed elsewhere.

C. ✅ Correct — members of the wheel group can use sudo when allowed in /etc/sudoers.

D. ❌ Activity monitoring is done by audit or logging tools.

Question 6

How does polkit differ from sudo?

🔘 Options
A. polkit is used for command-line actions only
B. sudo is used for background processes
C. polkit checks GUI-based policy rules instead of sudoers
D. sudo requires no password while polkit does

Answer 6

✅ Correct Answer
C. polkit checks GUI-based policy rules instead of sudoers

💡 Explanation
A. ❌ polkit is mostly for GUI/background actions.

B. ❌ sudo is used by the user on CLI, not by background processes.

C. ✅ Correct — polkit uses its own rules separate from /etc/sudoers.

D. ❌ Both may require passwords depending on system config.

Question 7

What is the purpose of the pkexec command?

🔘 Options
A. To check file permissions
B. To reboot the system
C. To run commands as another user using Polkit
D. To open a shell as root using sudo

Answer 7

✅ Correct Answer
C. To run commands as another user using Polkit

💡 Explanation
A. ❌ Use ls -l or stat to check file permissions.

B. ❌ Use reboot or shutdown, not pkexec.

C. ✅ Correct — pkexec uses Polkit to elevate permissions like sudo.

D. ❌ sudo -i opens a root shell — not pkexec.

Question 8

What does the command /sbin/shutdown -h now do in Linux?

🔘 Options
A. It creates a new shutdown configuration file
B. It halts (shuts down) the system immediately
C. It displays system uptime
D. It restarts the system

Answer 8

✅ Correct Answer
B. It halts (shuts down) the system immediately

💡 Explanation
A. ❌ No configuration file is created.

B. ✅ Correct — -h means halt, and now means immediately.

C. ❌ Use uptime or w for that.

D. ❌ To restart, you’d use reboot, not shutdown -h.

Question 9

Why do most commands in /sbin/ require sudo or root privileges?

🔘 Options
A. They are not executable by any user
B. They handle non-critical background tasks
C. They can affect system-wide settings or stability
D. They only work inside user home directories

Answer 9

✅ Correct Answer
C. They can affect system-wide settings or stability

💡 Explanation
A. ❌ They are executable but restricted to privileged users.

B. ❌ They handle critical tasks, not background ones.

C. ✅ Correct — commands like shutdown, fsck, and iptables need elevated privileges.

D. ❌ These commands are system-wide, not limited to home directories.

Question 10

Which of the following commands typically resides in /sbin/ and requires sudo?

🔘 Options
A. ls
B. reboot
C. nano
D. cat

Answer 10

✅ Correct Answer
B. reboot

💡 Explanation
A. ❌ ls is in /bin or /usr/bin, used by regular users.

B. ✅ Correct — reboot is a system-level command and requires sudo.

C. ❌ nano is a text editor, generally doesn’t need sudo.

D. ❌ cat is used to read file contents and is user-level.

Question 11

What does which shutdown return on most Linux systems?

🔘 Options
A. The shutdown history of the system
B. A man page with shutdown instructions
C. The full path to the shutdown binary
D. A configuration script for shutdown

Answer 11

✅ Correct Answer
C. The full path to the shutdown binary

💡 Explanation
A. ❌ last or journalctl would show shutdown history.

B. ❌ man shutdown would show documentation.

C. ✅ Correct — which shows where the command is stored (usually /sbin/shutdown).

D. ❌ There’s no script output; it’s a binary location.

Question 12

Which command is used to check and repair file systems in Linux and typically lives in /sbin/?

🔘 Options
A. mount
B. fsck
C. lsblk
D. findmnt

Answer 12

✅ Correct Answer
B. fsck

💡 Explanation
A. ❌ mount mounts file systems, not repairs them.

B. ✅ Correct — fsck (file system check) is a repair tool and requires sudo.

C. ❌ lsblk lists block devices, not for repair.

D. ❌ findmnt shows mounted filesystems but doesn’t repair.

Question 13

Where are most user-level commands like ls, cp, mv, and curl stored?

🔘 Options
A. /sbin
B. /etc
C. /usr/bin
D. /boot

Answer 13

✅ Correct Answer
C. /usr/bin

💡 Explanation
A. ❌ /sbin is for administrative tools.

B. ❌ /etc stores config files, not binaries.

C. ✅ Correct — /usr/bin holds standard user-level commands.

D. ❌ /boot contains bootloader files and kernels.

Question 14

Which /usr/bin command requires sudo only when modifying files owned by another user?

🔘 Options
A. mv
B. chown
C. cat
D. echo

Answer 14

✅ Correct Answer
B. chown

💡 Explanation
A. ❌ mv usually doesn’t require sudo unless you’re writing to protected areas.

B. ✅ Correct — chown (change ownership) requires elevated permissions for files you don’t own.

C. ❌ cat is a read-only command.

D. ❌ echo prints to screen or files you have write access to.

Question 15

Which /usr/bin command may require sudo if stopping a process you don’t own?

🔘 Options
A. top
B. kill
C. ps
D. uptime

Answer 15

✅ Correct Answer
B. kill

💡 Explanation
A. ❌ top is just for viewing.

B. ✅ Correct — kill can only stop your own processes unless you use sudo.

C. ❌ ps is for viewing processes.

D. ❌ uptime shows how long the system has been running.

Question 16

What does the useradd -D command do in Linux?

🔘 Options
A. Deletes a default user account
B. Displays or sets default user creation values
C. Deletes all user passwords
D. Displays disk usage for each user

Answer 16

✅ Correct Answer
B. Displays or sets default user creation values

💡 Explanation
A. ❌ The -D flag doesn’t delete users.

B. ✅ Correct — useradd -D shows or modifies the system-wide defaults for new users (e.g., shell, home path).

C. ❌ Passwords are managed with passwd or chage.

D. ❌ Use du or quota for disk usage info.

Question 17

What is the purpose of the SKEL field in useradd -D defaults?

🔘 Options
A. Stores user email settings
B. Specifies shell encryption method
C. Defines which default files are copied into new user home directories
D. Controls the shell version used by users

Answer 17

✅ Correct Answer
C. Defines which default files are copied into new user home directories

💡 Explanation
A. ❌ Not related to email.

B. ❌ Encryption methods are defined elsewhere, like in /etc/login.defs.

C. ✅ Correct — /etc/skel contains default config files (e.g., .bashrc) that are copied to new users’ home folders.

D. ❌ The shell is defined with the SHELL field.

Question 18

If the default shell is set using sudo useradd -D -s /bin/zsh, what will happen?

🔘 Options
A. All existing users will be switched to Zsh
B. All future users will have /bin/zsh as their login shell
C. The Zsh package will be installed automatically
D. No changes will occur until /etc/shadow is edited

Answer 18

✅ Correct Answer
B. All future users will have /bin/zsh as their login shell

💡 Explanation
A. ❌ Only new users are affected, not existing ones.

B. ✅ Correct — this sets Zsh as the default shell for users created after this change.

C. ❌ Shell packages must be installed manually.

D. ❌ /etc/shadow controls password settings, not shell.

Question 19

Why is it unsafe to manually edit /etc/passwd?

🔘 Options
A. It causes file permissions to change
B. It may corrupt system logs
C. It can break user records and affect login ability
D. It deletes the user if you make a typo

Answer 19

✅ Correct Answer
C. It can break user records and affect login ability

💡 Explanation
A. ❌ Permissions are not auto-altered by editing.

B. ❌ Not directly related to logs.

C. ✅ Correct — manual edits can introduce syntax errors that prevent users from logging in.

D. ❌ Typos may break things but won’t auto-delete accounts.

Question 20

Why were password hashes moved from /etc/passwd to /etc/shadow?

🔘 Options
A. To reduce disk usage
B. To allow users to see their own passwords
C. Because /etc/passwd is world-readable
D. To speed up the boot process

Answer 20

✅ Correct Answer
C. Because /etc/passwd is world-readable

💡 Explanation
A. ❌ File size wasn’t the issue.

B. ❌ Showing passwords is a security flaw.

C. ✅ Correct — since any user can read /etc/passwd, password hashes were moved to /etc/shadow, which is restricted.

D. ❌ This change wasn’t about boot speed.

Question 21

Which file stores hashed user passwords and password expiration info in modern Linux systems?

🔘 Options
A. /etc/group
B. /etc/passwd
C. /etc/skel
D. /etc/shadow

Answer 21

✅ Correct Answer
D. /etc/shadow

💡 Explanation
A. ❌ /etc/group stores group memberships.

B. ❌ No longer stores hashed passwords.

C. ❌ /etc/skel contains default files for new user home directories.

D. ✅ Correct — /etc/shadow securely stores password hashes and expiration info.

Question 22

What does the -D option do in the useradd command?

🔘 Options
A. Deletes a user account
B. Disables password login
C. Views or sets default user creation settings
D. Displays disk usage

Answer 22

✅ Correct Answer
C. Views or sets default user creation settings

💡 Explanation
A. ❌ Use userdel to delete users.

B. ❌ passwd -l locks login, not useradd -D.

C. ✅ Correct — useradd -D controls system-wide defaults like shell and home base.

D. ❌ Use du for disk usage.

Question 23

What happens if INACTIVE=-1 is set in useradd -D?

🔘 Options
A. Password never expires
B. Account is disabled immediately after password expiration
C. Account is never disabled, even after password expires
D. Account is locked after 1 day

Answer 23

✅ Correct Answer
C. Account is never disabled, even after password expires

💡 Explanation
A. ❌ Expiry and inactivity are different.

B. ❌ That would be a 0, not -1.

C. ✅ Correct — -1 means no auto-disable after password expiry.

D. ❌ Not a valid setting here.

Question 24

What does the -m flag in useradd -m username do?

🔘 Options
A. Changes the user’s password
B. Creates a mail account
C. Creates a home directory and copies default files
D. Makes the user a system admin

Answer 24

✅ Correct Answer
C. Creates a home directory and copies default files

💡 Explanation
A. ❌ Passwords are set using passwd.

B. ❌ Mail creation is separate.

C. ✅ Correct — -m sets up /home/username with contents from /etc/skel.

D. ❌ Admin privileges require group/sudoer configuration.

Question 25

What is the function of the SKEL=/etc/skel directory? 🔘 Options A. Stores system logs B. Contains default config files copied to new home directories C. Stores user passwords D. Sets user permissions

Answer 25

✅ Correct Answer B. Contains default config files copied to new home directories 💡 Explanation A. ❌ Logs are in /var/log. B. ✅ Correct — /etc/skel is a template for new users. C. ❌ Passwords are in /etc/shadow. D. ❌ Permissions are set using chmod or chown.

Question 26

Where are secure hashed passwords stored in modern Linux systems? 🔘 Options A. /etc/passwd B. /etc/login.defs C. /etc/shadow D. /etc/skel

Answer 26

✅ Correct Answer C. /etc/shadow 💡 Explanation A. ❌ Used to store hashes but is now public/readable. B. ❌ Sets password policy, not passwords themselves. C. ✅ Correct — /etc/shadow is secure and root-only. D. ❌ For copying default user files.

Question 27

What does sudo !! do? 🔘 Options A. Repeats the last command with elevated privileges B. Shows previous users C. Reloads system daemons D. Logs out the user

Answer 27

✅ Correct Answer A. Repeats the last command with elevated privileges 💡 Explanation A. ✅ Correct — helpful when you forgot to prefix a command with sudo. B. ❌ Use last for that. C. ❌ Use systemctl daemon-reexec for that. D. ❌ Use logout or exit.

Question 28

What does the chage command manage? 🔘 Options A. File permissions B. User login shell C. Password aging policies D. Group ownership

Answer 28

✅ Correct Answer C. Password aging policies 💡 Explanation A. ❌ That’s chmod. B. ❌ That’s usermod. C. ✅ Correct — chage adjusts max days, warnings, etc. D. ❌ Use chgrp or chown.

Question 29

What does passwd -l username do? 🔘 Options A. Locks the user's files B. Logs the user out immediately C. Locks the account by disabling password login D. Deletes the user

Answer 29

✅ Correct Answer C. Locks the account by disabling password login 💡 Explanation A. ❌ Doesn’t affect files. B. ❌ Doesn’t log out sessions. C. ✅ Correct — adds a ! in /etc/shadow. D. ❌ Use userdel to remove users.

Question 30

Question: What is the purpose of the -g flag when using the groupadd command? Options: A) Automatically assigns a name to the group B) Assigns a custom Group ID (GID) C) Grants admin rights to the group D) Adds the group to /etc/passwd

Answer 30

Answer: B) Assigns a custom Group ID (GID) Explanation: A) Incorrect — group names must be set manually. B) ✅ Correct — -g is used to set a specific GID, helpful for consistent user permissions across systems. C) Incorrect — admin rights aren't managed through groupadd. D) Incorrect — /etc/group is where group info is stored, not /etc/passwd.

Question 31

Question: How does the -f option affect the groupadd command? Options: A) Forces the group to be deleted B) Ignores errors if the group already exists C) Fixes permissions for the group D) Finds and displays existing group members

Answer 31

Answer: B) Ignores errors if the group already exists Explanation: A) Incorrect — that would relate to groupdel, not groupadd. B) ✅ Correct — -f tells groupadd not to throw an error if the group already exists. C) Incorrect — permissions are managed separately with chmod or chown. D) Incorrect — this is unrelated to group creation.

Question 32

Question: Which option must be used with -o to allow duplicate GIDs? Options: A) -n B) -f C) -g D) -r

Answer 32

Answer: C) -g Explanation: A) Incorrect — -n isn’t a valid option in groupadd. B) Incorrect — -f is for ignoring errors, not related to duplicate GIDs. C) ✅ Correct — -o only works if you're specifying a GID using -g. D) Incorrect — -r is used to create system groups, not related to duplication.

Question 33

Question: What is the correct and safe way to add a user to a new group without removing them from existing group memberships? Options: A) usermod -G groupname username B) usermod -aG groupname username C) adduser username groupname D) groupmod -a username groupname

Answer 33

Answer: B) usermod -aG groupname username Explanation: A) ❌ This replaces the user’s current groups. B) ✅ Correct — -a (append) and -G (group) ensures the user is added safely. C) ❌ Not the proper syntax in all distros. D) ❌ Invalid command; groupmod is for modifying group properties, not users.

Question 34

Question: What does the -a option do when used with the usermod command? Options: A) Automatically assign a primary group B) Append the user to additional groups without removing current ones C) Assign the user admin privileges D) Set account expiration time

Answer 34

Answer: B) Append the user to additional groups without removing current ones Explanation: A) ❌ Primary group is handled with -g. B) ✅ Correct — -a ensures no existing group memberships are lost. C) ❌ Admin rights come from group membership like sudo. D) ❌ That would be managed by chage.

Question 35

Question: What happens if you run sudo usermod -G devteam mousa without the -a flag? Options: A) The user is safely added to the devteam group B) Nothing happens unless the user exists C) The user is removed from all groups except devteam D) The user's shell is changed

Answer 35

Answer: C) The user is removed from all groups except devteam Explanation: A) ❌ Not safely — this removes all previous groups. B) ❌ The user must exist, but that’s not the issue here. C) ✅ Correct — without -a, -G replaces group memberships. D) ❌ Shell changes use -s.

Question 36

Question: What is the primary purpose of the last command in Linux? Options: A) To display active processes B) To list the most recent login and reboot events C) To terminate user sessions D) To switch users

Answer 36

Answer: B) To list the most recent login and reboot events Explanation: A) ❌ That’s what top or ps is for B) ✅ Correct — last reads from /var/log/wtmp to show login/logout/reboot history C) ❌ kill or pkill is used to terminate sessions D) ❌ su or sudo switches users

Question 37

Question: From which file does the last command retrieve its information? Options: A) /etc/passwd B) /var/log/auth.log C) /var/log/wtmp D) /etc/login.defs

Answer 37

Answer: C) /var/log/wtmp Explanation: A) ❌ /etc/passwd stores user account info B) ❌ Authentication logs, not session history C) ✅ Correct — this binary file logs login/logout events D) ❌ That file stores password and user account policy

Question 38

Question: What does the terminal label pts/0 represent in the output of the last command? Options: A) A local keyboard login B) A graphical login session C) A remote login terminal (like SSH) D) A reboot message

Answer 38

Answer: C) A remote login terminal (like SSH) Explanation: A) ❌ Local login would be shown as tty1 B) ❌ Graphical sessions aren’t labeled like this C) ✅ Correct — pts/0 is a pseudo-terminal often associated with remote access like SSH D) ❌ Reboots appear as "reboot" in the user column

Question 39

Question: In the last command output, what does the entry reboot system boot indicate? Options: A) A user manually restarted their session B) A failed login attempt C) The system was restarted D) A new user account was added

Answer 39

Answer: C) The system was restarted Explanation: A) ❌ This isn’t about a user session B) ❌ That would show in authentication logs C) ✅ Correct — reboot logs system restarts D) ❌ Not related to user account management

Question 40

Q: What is the purpose of the .bashrc file in a Linux system, and when does it get executed? Options: A. It configures the user's environment at every system boot. B. It’s a hidden file that runs when a user logs in via SSH. C. It’s a hidden file that runs every time a new interactive terminal session is opened. D. It stores system-wide PATH variables and executes only during system updates.

Answer 40

Explanation: A is incorrect – system boot processes are handled by systemd, not .bashrc. B is incorrect – SSH login triggers .bash_profile, not .bashrc. ✅ C is correct – .bashrc is executed every time an interactive shell is opened, such as a terminal window or tab. D is incorrect – PATH variables can be set in .bashrc, but it’s not exclusive to system updates or system-wide usage.

Question 41

Q: What types of customizations are commonly added to a user's .bashrc file? Options: A. Kernel module settings and device driver configurations B. Aliases, environment variables, prompt appearance, and custom PATHs C. Service startup commands like Apache or MySQL D. Disk partitioning schemes and bootloader configs

Answer 41

Explanation: A is incorrect – kernel modules are managed with tools like modprobe, not .bashrc. ✅ B is correct – .bashrc is used for defining command aliases, setting environment variables, customizing the prompt (PS1), and appending directories to PATH. C is incorrect – service management is done through systemctl or init scripts, not .bashrc. D is incorrect – bootloader configs are part of /boot or /etc/default/grub, unrelated to .bashrc.

Question 42

Q: How can a user apply changes made in their .bashrc file without restarting the terminal? Options: A. Restart the shell using reboot-shell B. Execute the command source ~/.bashrc or . ~/.bashrc C. Open a new browser window D. Kill the terminal process and reopen it

Answer 42

Explanation: A is incorrect – reboot-shell is not a valid command. ✅ B is correct – source ~/.bashrc (or . ~/.bashrc) reloads the file in the current session, applying any changes immediately. C is incorrect – opening a browser has nothing to do with shell configuration. D is partially effective – closing and reopening a terminal will apply .bashrc, but it’s less efficient than sourcing it.

Question 43

Q: When is the .bash_profile file executed in a Linux system? Options: A. Every time a new terminal tab is opened B. During login shell sessions, like SSH or TTY C. When the system is shutting down D. When .bashrc is missing or corrupted

Answer 43

Explanation: A is incorrect – terminal tabs launch interactive shells that use .bashrc. ✅ B is correct – .bash_profile is used for login shells such as SSH or virtual consoles (TTY). C is incorrect – shutdown processes are unrelated to .bash_profile. D is incorrect – .bash_profile doesn’t serve as a fallback for .bashrc; in fact, it often explicitly sources .bashrc.

Question 44

What is the key difference between ~/.bashrc and /root/.bashrc in a Linux system? (Choose the best answer) A. They are identical and used by all users B. ~/.bashrc is for the current user, /root/.bashrc is for the root user C. They both serve only to change graphical login settings D. /root/.bashrc is copied automatically from ~/.bashrc at login

Answer 44

✅ Correct Answer: B 📘 Explanation: B is correct: ~/.bashrc belongs to regular users, while /root/.bashrc is the root user's shell configuration file. Each file controls the shell behavior for its respective user. A is incorrect: They are not shared; each user has their own .bashrc. C is incorrect: These files are for terminal shell configuration, not graphical login. D is incorrect: The system does not auto-copy .bashrc from one user to another.

Question 45

Why might an alias defined in ~/.bashrc not work when switching to root with sudo -i? A. Because the shell ignores aliases B. Because root's environment does not use .bashrc C. Because aliases must be defined in /root/.bashrc to apply when logged in as root D. Because sudo blocks all user-level configuration

Answer 45

✅ Correct Answer: C 📘 Explanation: C is correct: When using sudo -i, you start a login shell as root, which uses /root/.bashrc. If the alias isn’t defined there, it won’t exist for the root user. A is incorrect: Shells do use aliases when properly defined. B is incorrect: Root does use .bashrc, but its own (/root/.bashrc). D is incorrect: sudo does not block aliases; it simply doesn’t load .bashrc unless invoked with -i.

Question 46

Which command ensures that root's .bashrc is loaded when switching to the root environment? A. sudo su B. sudo -i C. sudo bash D. su -c

Answer 46

✅ Correct Answer: B 📘 Explanation: B is correct: sudo -i starts a login shell, loading /root/.bashrc if it exists. A is incorrect: sudo su doesn’t guarantee loading a login shell unless used with -l. C is incorrect: Starts a non-login shell. D is incorrect: Runs a single command as another user, not a full login shell.

Question 47

What is the function of the $PATH variable set in .bash_profile or .profile? A. Defines user interface themes B. Stores backup scripts C. Tells Linux where to find executable commands D. Enables root permissions automatically

Answer 47

✅ Correct Answer: C 📘 Explanation: C is correct: $PATH defines which directories Linux searches when you type a command like ls. A is incorrect: Themes are unrelated to $PATH. B is incorrect: It’s not for storing files. D is incorrect: It has nothing to do with privileges.