LFCS Essential Commands Practice Test 2 — 15 Questions

Question 1

A user with uid 1000 tries to read /etc/shadow and gets 'Permission denied'. The user is not in the shadow group. Which of the following actions would allow the user to read the file without changing the file's group or permissions?

Accepted Answer

Add user1 to the shadow group using usermod -aG shadow user1. Option C is correct because adding user1 to the shadow group grants group-level read access to /etc/shadow without altering the file's permissions or group ownership. The file is typically owned by root:shadow with permissions 640 (rw-r-----), so members of the shadow group can read it. The usermod -aG command appends the user to the supplementary group, preserving existing group memberships.

Answer

Set an ACL using setfacl to grant user1 read access

Answer

Use chmod o+r /etc/shadow as root

Answer

Change the file owner to user1 using chown

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. Option B is correct because 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/.. Option C is correct because 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. Option B is correct because `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. Option A is correct because 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 system administrator runs 'grep -r 'error' /var/log' and gets many false positives. They want to search only for the exact word 'error' as a whole word, case-insensitively, and display line numbers. Which command should they use?

Accepted Answer

grep -rwin 'error' /var/log. Option D is correct because it combines all required flags: `-r` for recursive search, `-w` for whole-word matching (using word boundaries), `-i` for case-insensitive search, and `-n` for displaying line numbers. The `-w` flag ensures that only the exact word 'error' is matched, not substrings like 'error404' or 'error-prone', which eliminates false positives.

Answer

grep -rwi 'error' /var/log

Answer

grep -rin 'error' /var/log

Answer

grep -rwn 'error' /var/log

Question 7

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. Option A is correct because `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 8

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. Option A is correct because 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 9

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. Option A is correct because 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 10

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--' correspond to owner: rwx (7), group: r-x (5), others: r-- (4). The octal value 754 is derived by summing the binary bits for each triad: read (4), write (2), execute (1). Thus, chmod 754 sets the exact permissions requested.

Answer

755

Answer

744

Question 11

Order the steps to mount an ext4 filesystem from an external USB drive automatically at boot.

Question 12

Match each Linux permission type to its symbolic representation.

Question 13

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 14

A system administrator needs to find all files under /var/log that have been modified within the last 7 days. Which command accomplishes this task?

Accepted Answer

find /var/log -mtime -7. Option C is correct because the `find` command with `-mtime -7` searches for files whose content was modified (i.e., changed) within the last 7 days. The `-mtime` flag uses a 24-hour period, so `-7` means files modified less than 7 days ago, which matches the requirement to find files modified within the last 7 days under /var/log.

Answer

find /var/log -atime -7

Answer

find /var/log -mmin -10080

Answer

find /var/log -ctime -7

Question 15

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. The correct answer is A: 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

LFCS Essential Commands Practice Test 2 — 15 Questions

Exhibit

LFCS Essential Commands Practice Test 2 — 15 Questions

Exhibit