Linux Operations Quiz: Answers and Explanations for Sysadmin Fundamentals

Multiple‑Choice Questions (Non‑single choice)

1. In regular expressions, which character class represents a non‑space character?
   a. [:graph:]
   b. [:digit:]
   c. [:space:]
   d. [:alpha:]
   Answer: a

2. Which statement about Bash variables is correct?
   a. Can be set in /etc/profile for all users permanently
   b. Adding to ~/.bash_profile affects a single user temporarily
   c. Using export defines it for the current shell permanently
   d. All statements are incorrect
   Answer: a

3. After logging into Linux, the shell reads startup files in which order?
   a. /etc/profile → ~/.bash_profile → ~/.profile → ~/.bash_login
   b. /etc/profile → ~/.bash_profile → ~/.bash_login → ~/.profile
   c. ~/.bash_profile → /etc/profile → ~/.profile → ~/.bash_login
   d. ~/.bash_login → ~/.profile → ~/.bash_profile → /etc/profile
   Answer: b

4. Command to create multi‑level directories:
   a. mkdir -p
   b. mkdir -v
   c. mkdir -m
   d. mkdir -Z
   Answer: a

5. Which command can inspect attributes of a file that even root cannot modify directly?
   a. ls -lh
   b. file
   c. stat
   d. lsattr
   Answer: d

6. Which alias definition is correct?
   a. LS='ls -lh'
   b. set cnet 'cd /etc/sysconfig/network-scripts/ifcfg-eth0'
   c. alias die='rm -fr'
   d. unalias die='rm -fr'
   Answer: c

7. Common text‑editing tools include:
   a. nano
   b. cat
   c. cut
   d. vim
   Answer: a, d

8. In the find command, which option selects socket files?
   a. d
   b. l
   c. p
   d. s
   Answer: d

9. After applying chmod g+s to a file with mode -rw-r--r--, the resulting mode is:
   a. -rw-r-Sr--
   b. -rw-r-sr--
   c. -rw-r--r--
   d. -rw-r-xr--
   Answer: a

10. LVM partition type identifier for fdisk is:
    a. l
    b. lvm
    c. 9e
    d. 8e
    Answer: d

11. Command to archive a directory without compression using tar:
    a. tar -cvf
    b. tar -zcvf
    c. tar -jvf
    d. tar -jcvf
    Answer: a

12. Which positional parameter represents the script itself?
    a. $0
    b. $1
    c. $#
    d. $@
    Answer: a

13. The four‑layer and seven‑layer load balancing correspond to which OSI layers?
    a. Transport, Presentation
    b. Network, Application
    c. Transport, Application
    d. Network, Presentation
    Answer: c

14. To give process 119 higher CPU priority than process 110, you should:
    a. nice -5 119
    b. renice -5 119
    c. nice -5 110
    d. renice -5 110
    Answer: b

15. To add a crontab entry for user magedu non‑interactively:
    a. Write to /var/spool/cron/root
    b. Write to /var/spool/cron/magedu
    c. Write to /var/spool/root/cron
    d. Write to /var/spool/magedu/cron
    Answer: b

16. Command to start network service on CentOS 7:
    a. service network start
    b. /etc/init.d/network start
    c. systemctl start network.service
    d. /etc/init.d/rc.d/init.d start
    Answer: c

17. During kernel self‑initialization, which task is performed?
    a. Detect all recognizable hardware
    b. Mount the real root filesystem read‑only
    c. Search boot devices sequentially, using the first with a bootloader
    d. Launch the first user‑space program (/sbin/init)
    Answer: c

18. Which runlevel description for CentOS 6 is incorrect?
    a. 4 – maintenance mode, multi‑user, network enabled, no NFS
    b. 1 – single‑user, no authentication required for root
    c. 3 – normal multi‑user text mode
    d. 5 – normal multi‑user graphical mode
    Answer: a

19. Command to output the line containing the root user from /etc/passwd:
    a. awk '{if($1=/root/) print }' /etc/passwd
    b. awk -F: '{if($1==/root/) print }' /etc/passwd
    c. awk -F: '{if($1=/root/) print }' /etc/passwd
    d. awk -F: '{if($1~/root/) print }' /etc/passwd
    Answer: d

20. Which is NOT a function of /etc/rc.d/rc.sysinit?
    a. Set hostname from configuration
    b. Configure server IP address
    c. Print welcome text
    d. Activate LVM and RAID devices
    Answer: b

True/False Questions (Analyze why they are right or wrong)

1. Symmetric encryption uses the same key for encryption and decryption, with main algorithms md5, sha1.
   Answer: False – md5 and sha1 are one‑way hash algorithms, not symmetric encryption.

2. After implementing RAID 1, overall write performance degrades.
   Answer: True

3. RAID 5 requires at least three disks.
   Answer: True

4. keepalived is implemented based on the VRRP protocol.
   Answer: True

5. If the system limit for open file descriptors is raised from 1024 to 65535, a child process of a program that started before the change will still have a limit of 1024.
   Answer: False

Short‑Answer Questions

1. Find ordinary files or directories in the current directory that have not been modified in the last 10 days and are larger than 4 KB.
   Answer: find ./ -type d -o -type f -size +4k ! -mtime -10

2. Use ss to list connections in TIME_WAIT state.
   Answer: ss -4 state time-wait   or   ss -o state time-wait

3. Briefly describe the boot process of CentOS 6.
   Answer: POST → BIOS (boot sequence) → MBR (bootloader) → kernel (initramfs) → /sbin/init → set default runlevel → run /etc/rc.d/rc.sysinit for system initialization → start services for the runlevel → start console → start graphical interface if runlevel 5 → display login prompt.

4. Difference between yum update and yum upgrade.
   Answer: yum update upgrades packages and also upgrades the system kernel and core components; yum upgrade only upgrades packages without touching the kernel or core system.

5. Schedule a script /data/get_username.sh to run at 01:05 every Tuesday and append its output to /tmp/get_username.log.
   Answer: 5 1 * * 2 /bin/sh /data/get_username.sh >> /tmp/get_username.log 2>&1