Top 100 Linux Command Quiz: Test Your Sysadmin Knowledge

Linux Commands and System‑Administration Quiz – Questions, Correct Answers, and Brief Explanations

What is the purpose of the cron daemon? D – Scheduling daily system tasks . Cron runs scheduled jobs defined in crontabs.

Which of the following is a block device on most Linux systems? B – Hard disk . Block devices provide buffered I/O and include disks and partitions.

Which command displays output one page at a time? C – more . It pauses after each screenful of text.

How can you find out how much space is left in the current directory? B – du . . du reports disk usage of the specified path.

Which command changes a file's permission settings? B – chmod . It modifies the read/write/execute bits.

How to determine which RPM package provides /etc/my.conf ? C – rpm -qf /etc/my.conf . The -qf query finds the owning package.

Switch from runlevel 3 to runlevel 5 without rebooting? B – telinit 5 . telinit changes the system's runlevel.

Command to change IDE hard‑disk settings? C – hdparm . It configures SATA/IDE drive parameters.

List tasks scheduled to run once at a specific future time? A – atq . It shows the pending at jobs.

Effect of set PS1="[\u\w\t]$"; export PS1 ? B – Changes the command prompt . PS1 defines the primary shell prompt.

Where to place a default .bashrc for new users? A – /etc/skel/ . Files in this directory are copied to new home directories.

Purpose of the export command in bash? C – Sets environment variables for other programs . Exported variables are inherited by child processes.

Correct permissions for /etc/passwd and /etc/shadow on a shadow‑password system? C – -rw-r--r-- for /etc/passwd , -r-------- for /etc/shadow .

Parameter to delete a user and also remove the user's home directory? C – userdel -r . The -r flag removes the home directory.

Crontab entry to run mybackup at 1 PM and 8 PM Monday‑Friday? B – 0 13,20 * * 1,2,3,4,5 mybackup .

Command to unmount a currently mounted filesystem? A – umount . It detaches the filesystem from the mount point.

Default file permissions for a newly created file when umask is 022? D – rw-r--r-- . The umask removes write permission for group and others.

How to locate the binary path of Xconfigurator ? D – which Xconfigurator . which searches the PATH.

Command to mount all filesystems defined in /etc/fstab ? B – mount -a .

After creating a symbolic link new → old , if old is deleted, can the data still be accessed via new ? B – Yes . The symlink points to the inode; if the inode is removed, the link becomes dangling.

Default percentage of space reserved for the root user on ext2/3/4 filesystems? C – 10% .

Command to show inode usage per partition? A – df -i .

Runlevel that provides a graphical interface on most Linux distributions? D – 5 .

Find all manual pages containing the word "print"? D – apropos print .

What does man 5 passwd display? B – The structure of the passwd file (section 5 of the manual).

Command to list lines starting with an asterisk (*) in a file? D – grep '^\*' file .

Which ps option shows processes of all users? D – -x .

Command to display the contents of a binary file? A – od (octal dump).

How to count the number of registered users (including system accounts) on a Linux system? D – wc --lines /etc/passwd .

Character that indicates line continuation in a shell script? B – Backslash ( \ ) .

Effect of kill 9 ? C – Sends SIGKILL to the process with PID 9 . SIGKILL cannot be caught.

Command to remove a non‑empty directory /tmp ? B – rm -rf /tmp .

Schedule cmd1 to run at midnight today? D – echo "cmd1" | at midnight .

Correct order for restoring from incremental backups? A – Restore the last full backup first, then apply incremental backups from oldest to newest.

File to edit for setting environment variables for all users? B – /etc/profile .

How to bypass an alias for ls and use the original command? A – \ls . The leading backslash disables alias expansion.

Correct shebang line for a Linux shell script? B – #!/bin/sh .

Syntax to run cmd2 only if cmd1 succeeds? A – cmd1 && cmd2 .

File that defines I/O ports of network cards? C – /proc/ioports .

Software that provides TCP/IP packet filtering on Linux? C – iptables .

Command to pause a print queue? C – lpc (line printer control).

Vi command to exit without saving? D – :q! .

Default font server for XFree86 3.x? A – xfs .

Command to test basic network connectivity? A – ping .

Protocol that uses more than one port? B – FTP (uses separate control and data ports).

PPP authentication protocol that does NOT transmit passwords in clear text? D – CHAP .

Filesystem that should be allocated the most space on a typical Linux system? A – /usr (holds most applications and libraries).

How to install an RPM package on a Debian system? D – alien pkgname.rpm ; dpkg -i pkgname.deb . alien converts the package.

Step in software installation that requires root privileges? D – make install .

Command to update already‑installed RPM packages? B – rpm -F *.rpm (freshen updates only if newer).

Where should LILO be installed on a dual‑boot Linux/Windows system? A – MBR (Master Boot Record) .

Configuration file for ldconfig ? B – /etc/ld.so.conf .

Command to create a .tar.gz archive? C – tar -czvf filename.tgz * .

Daemon that provides network services (e.g., inetd)? D – inetd .

Daemon needed for Linux‑Windows file sharing? B – smbd (Samba daemon).

Default user for Apache child processes? D – nobody .

Default location where sendmail stores undelivered mail? B – /var/spool/mail/ .

Main configuration file for Apache? A – httpd.conf .

Directory where kernel module parameters such as I/O addresses are stored? D – /etc/sysconfig .

Command to disable mail notifications (biff)? A – biff n .

Effect of pressing Control‑Z while a command runs in bash? B – Sends the job to the background (SIGTSTP).

Files that define the user environment in bash? D – .bashrc and .bash_profile .

Command to show shared libraries used by a program? A – ldd .

How to view configuration files of an installed RPM package? A – rpm -qc rpm1 .

Command to display the changelog of an RPM package? C – rpm --changelog postfix .

Makefile target that installs compiled code? D – make install .

Command to extract a .tar.gz archive? B – tar -xzvf filename.tgz .

Section in XF86Config that sets the font file? A – The Fonts section.

What does “8‑bit color” refer to? C – 256 colors .

File that sets the X window display resolution? D – XF86Config .

Environment variable that specifies the X server for remote X applications? A – DISPLAY .

In xdm’s configuration directory, which file defines applications started after a user logs in? A – Xsession (and Xsetup_0 for early setup).

If netstat -a hangs, which subsystem is likely the problem? B – DNS resolution.

Protocol used by ping ? D – ICMP .

Command NOT used for network troubleshooting? B – init (system initialization, not a network tool).

Protocol typically used for dial‑up networking? A – PPP .

Protocol that provides automatic IP address allocation? C – DHCP .

File that defines network service ports? B – /etc/services .

Command to generate a checksum for a file? D – md5sum .

Default location for user mail files? D – /var/spool/mail/ .

File containing the directory list used by the NFS daemon? C – /etc/exports .

How to stop the telnet service on a machine? D – Comment the telnet entry in /etc/xinetd.conf .

File that stores sendmail aliases? A – /etc/aliases .

Configuration file for smbd and nmbd daemons? B – /etc/smb.conf .

Command to unload a kernel module? A – rmmod .

When must you run lilo ? C – After installing a new kernel.

Command to list all loaded kernel modules? A – lsmod .

Command to clear a printer queue? B – lprm - (removes all jobs).

Command to show interrupts used by a network card? B – cat /proc/interrupts .