LFCS Essential Commands Practice Test 5 — 15 Questions

Question 1

Which THREE of the following commands can be used to view the contents of a compressed file named 'file.gz' without permanently decompressing it? (Choose exactly three.)

Accepted Answer

zmore file.gz. Option B (zmore file.gz) is correct because zmore is a filter that pipes the decompressed output of gzip-compressed files through more, letting you page through the contents without writing a decompressed file to disk. Option D (zcat file.gz) is correct because zcat decompresses the file to standard output, displaying its contents on screen while leaving the original file.gz intact. Option E (zless file.gz) is correct because zless uses less to page through the decompressed stream of a gzip file, again without permanently decompressing it. Option A (gzip file.gz) is wrong because gzip is used to compress files (and would actually try to compress file.gz further), not to view contents. Option C (gunzip file.gz) is wrong because gunzip permanently decompresses the file, replacing file.gz with an uncompressed file, which is exactly what the question excludes.

Answer

gzip file.gz

Answer

gunzip file.gz

Question 2

You are a system administrator for a company that runs a web server on a Linux system. The web server logs are stored in /var/log/nginx/access.log. The log file grows rapidly and rotates weekly via logrotate. The system has been running for several months. Recently, the development team reported that the web server is responding slowly. You suspect that the disk I/O might be high due to log file activity. You check the disk usage and find that /var/log/nginx/access.log is 4 GB, and the rotated logs (access.log.1.gz, access.log.2.gz, etc.) total another 10 GB. The /var partition has 20 GB total, so it's 70% full. You decide to reduce the disk usage by compressing the current log file and truncating it without stopping the nginx service. Which command sequence should you use to safely achieve this?

Accepted Answer

cp /var/log/nginx/access.log /var/log/nginx/access.log.bak && :> /var/log/nginx/access.log && gzip /var/log/nginx/access.log.bak. It first copies the current log file to a backup, then truncates the original file in place using the shell null command (`:>`) without stopping nginx, and finally compresses the backup. This ensures nginx continues writing to the same inode (file descriptor remains valid) and the disk space is reclaimed after compression.

Answer

:> /var/log/nginx/access.log && cp /var/log/nginx/access.log /var/log/nginx/access.log.bak && gzip /var/log/nginx/access.log.bak

Answer

rm /var/log/nginx/access.log && touch /var/log/nginx/access.log && chmod 644 /var/log/nginx/access.log

Answer

mv /var/log/nginx/access.log /var/log/nginx/access.log.bak && touch /var/log/nginx/access.log && gzip /var/log/nginx/access.log.bak

Question 3

You are managing a Linux server that hosts a critical web application. The server is running low on disk space in the root filesystem, and you need to free up space urgently. You run 'df -h' and see that /dev/sda1 is mounted on / and is 95% full. You also notice that /var/log/messages is over 2 GB in size. The application writes logs to /var/log/app.log, which is also large. The server has a separate /var partition that has plenty of free space. The application must continue running with minimal downtime. You need to compress and rotate logs without losing any data, and ensure that the root filesystem has at least 10% free space. Which of the following actions should you take first to achieve this goal?

Accepted Answer

Use logrotate with the 'copytruncate' option to rotate /var/log/app.log and move the rotated file to /var/old_logs/.. Logrotate with the 'copytruncate' option allows the application to continue writing to the same file descriptor while the current log is copied and then truncated to zero length. This avoids any application downtime and the rotated log can be moved to the separate /var partition (which has free space) for compression or archiving, freeing space on the root filesystem without data loss.

Answer

Delete /var/log/app.log and /var/log/messages to free space quickly.

Answer

Stop the application, truncate /var/log/app.log, then restart the application.

Answer

Compress /var/log/app.log using gzip and keep it in place.

Question 4

A system administrator needs to list all files in the current directory, including hidden files, in a long listing format sorted by modification time (oldest first). Which command achieves this?

Accepted Answer

ls -lart. `ls -lart` combines the `-l` (long listing), `-a` (include hidden files starting with dot), `-r` (reverse order), and `-t` (sort by modification time, newest first). The reverse flag flips the sort to oldest first, meeting the requirement exactly.

Answer

ls -lihrt

Answer

ls -lat

Answer

ls -lrt

Question 5

A user wants to find all files in /var/log that have been modified within the last 2 days. Which command should they use?

Accepted Answer

find /var/log -mtime -2. The `find` command with `-mtime -2` searches for files whose content was last modified less than 2 days ago (i.e., within the last 48 hours). The minus sign before the number indicates 'less than' or 'within the last N days', which matches the user's requirement to find files modified within the last 2 days.

Answer

find /var/log -mmin -2880

Answer

find /var/log -mtime +2

Answer

find /var/log -mtime 2

Question 6

A user needs to view the contents of a compressed log file /var/log/syslog.gz without first decompressing it. Which command should they use?

Accepted Answer

zcat /var/log/syslog.gz. `zcat` is specifically designed to read the contents of gzip-compressed files without permanently decompressing them. It decompresses the data on the fly and sends the output to stdout, allowing the user to view the log file's contents directly from the terminal.

Answer

gzip -d /var/log/syslog.gz

Answer

gunzip /var/log/syslog.gz

Answer

cat /var/log/syslog.gz

Question 7

A developer wants to change the ownership of a directory and all its contents recursively to user 'appuser' and group 'appgroup'. Which command accomplishes this?

Accepted Answer

chown -R appuser:appgroup /app. The `chown -R appuser:appgroup /app` command recursively changes both the user and group ownership of the `/app` directory and all its contents. The `-R` flag ensures recursion, and the colon-separated `user:group` syntax sets both ownership attributes in a single command.

Answer

chown -R appuser /app && chgrp appgroup /app

Answer

chgrp -R appgroup /app && chown appuser /app

Answer

chown -R appuser: /app && chgrp -R appgroup /app

Question 8

A systems administrator needs to add a new user 'jdoe' with a home directory in /export/home, a UID of 1500, and an expiry date of 2025-12-31. Which command should they use?

Accepted Answer

useradd -u 1500 -d /export/home/jdoe -e 2025-12-31 jdoe. The `useradd` command with `-u 1500` sets the UID, `-d /export/home/jdoe` explicitly specifies the home directory path (without creating it unless `-m` is also used), and `-e 2025-12-31` sets the account expiry date in YYYY-MM-DD format. This matches all requirements: UID 1500, home directory at /export/home/jdoe, and expiry on 2025-12-31.

Answer

useradd -u 1500 -d /export/home/jdoe -c 2025-12-31 jdoe

Answer

useradd -u 1500 -m -e 2025-12-31 jdoe

Answer

useradd -u 1500 -b /export/home -e 2025-12-31 jdoe

Question 9

A user wants to set the permissions of a file to 'rwxr-xr--'. Which octal permission value should they use with chmod?

Accepted Answer

754. The permissions 'rwxr-xr--' mean that the owner has read, write, and execute (rwx = 7), the group has read and execute (r-x = 5), and others have only read (r-- = 4). Therefore, the correct octal value is 754. Option A is correct. Option B (755) gives others execute, option C (644) gives owner no execute and group no execute, and option D (744) gives group no execute.

Answer

755

Answer

644

Answer

744

Question 10

Match each Linux permission type to its symbolic representation.

Accepted Answer

Read: r. In Linux, standard file permissions are represented by symbols: read (r), write (w), and execute (x). Each permission type maps to a unique symbol. Confusion often arises from swapping these symbols.

Answer

Read: w

Answer

Write: x

Answer

Execute: r

Question 11

A user reports that a shell script 'backup.sh' in /home/user/scripts fails to execute. What is the most likely cause?

Accepted Answer

The script does not have execute permission for the user.. The most likely cause is that the script lacks execute permission for the user. In Linux, a file must have the execute bit set (e.g., `chmod +x backup.sh`) to be run as a script. Without it, the shell will refuse to execute the file, even if the user has read access and the script is syntactically correct.

Answer

The script is not in the user's PATH.

Answer

The script must be owned by root.

Answer

The script does not have a shebang line (#!/bin/bash) at the top.

Question 12

A process is consuming 99% CPU and is unresponsive to normal shutdown requests. After running 'top', you see the PID is 1234. What is the most appropriate command to stop the process gracefully first?

Accepted Answer

kill -15 1234. Kill -15 1234. The SIGTERM signal (15) is the standard way to request a process terminate gracefully, allowing it to clean up resources, close files, and perform shutdown routines. This is the most appropriate first step before escalating to stronger signals, as it gives the process a chance to exit normally.

Answer

kill -19 1234

Answer

kill -2 1234

Answer

kill -9 1234

Question 13

A backup script must create a compressed archive of the /etc directory, preserving file permissions and timestamps. Which command should be used?

Accepted Answer

tar -czvf backup.tar.gz /etc. The `tar -czvf` command creates a compressed archive (via gzip) that preserves file permissions and timestamps by default when run as root. The `-c` flag creates the archive, `-z` compresses it with gzip, `-v` provides verbose output, and `-f` specifies the archive filename. Tar is the standard Unix tool for bundling files into a single archive while retaining metadata like ownership, permissions, and timestamps.

Answer

gzip -r /etc > backup.tar.gz

Answer

cpio -ov < /etc > backup.cpio

Answer

rsync -av /etc /backup/etc

Question 14

A user wants to continuously monitor a log file that is being written to by a running service. Which command achieves this?

Accepted Answer

tail -f /var/log/syslog. The `tail -f` command displays the last 10 lines of a file by default and then continues to output new lines as they are appended, making it ideal for real-time monitoring of a growing log file. The `-f` flag (follow) keeps the file open and polls for changes, typically using inotify on Linux, to output new data immediately.

Answer

head -20 /var/log/syslog

Answer

less /var/log/syslog

Answer

cat /var/log/syslog

Question 15

To check the disk usage of the /var/log directory in a human-readable format, which command is appropriate?

Accepted Answer

du -sh /var/log. The `du -sh /var/log` command is correct because `du` (disk usage) estimates file and directory space usage, and the `-s` option summarizes the total for the specified directory, while `-h` prints sizes in human-readable format (e.g., K, M, G). This directly answers the requirement to check disk usage of the /var/log directory in a human-readable form.

Answer

ls -lh /var/log

Answer

df -h /var/log

Answer

fdisk -l /var/log