LFCS Essential Commands Practice Test 3 — 15 Questions

Question 1

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 -mmin -10080. Options B and C are both correct because the `find` command can search for files modified within the last 7 days using either `-mtime -7` (modification time in days) or `-mmin -10080` (modification time in minutes, where 10080 minutes equals 7 days). Option A checks access time (`-atime`), not modification time. Option D checks change time (`-ctime`), which includes metadata changes. Therefore, both B and C achieve the task.

Answer

find /var/log -atime -7

Answer

find /var/log -ctime -7

Question 2

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 3

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 4

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 5

A system administrator needs to replace all occurrences of 'oldhost' with 'newhost' in /etc/hosts, but only on lines that contain the string 'domain'. Which sed command accomplishes this?

Accepted Answer

sed -i '/domain/s/oldhost/newhost/g' /etc/hosts. Options A and D are correct because they use `-i` for in-place editing, restrict substitution to lines containing 'domain' with `/domain/`, and use the `g` flag to replace all occurrences on each line. Option B is incorrect because it only outputs lines containing 'domain' to stdout but does not edit the file. Option C is incorrect because it lacks the `g` flag, replacing only the first occurrence per line. Option E is incorrect because `-n` suppresses default output and `p` prints only lines where substitution occurred, but the file is not modified.

Answer

sed 's/oldhost/newhost/g' /etc/hosts | grep domain

Answer

sed -i '/domain/s/oldhost/newhost/' /etc/hosts

Answer

sed -ne '/domain/s/oldhost/newhost/gp' /etc/hosts

Question 6

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

Question 7

A user needs to view the contents of a large text file one screen at a time. Which command is best for this?

Accepted Answer

less file.txt. `less` is a terminal pager that allows forward and backward navigation through a file, making it ideal for viewing large text files one screen at a time. Unlike `more`, `less` supports scrolling both up and down, and it does not load the entire file into memory, which is efficient for large files.

Answer

nl file.txt

Answer

more file.txt

Answer

cat file.txt

Question 8

A cron job runs a script every hour but sometimes fails because the script cannot find commands like 'tar' and 'gzip'. The script works when run manually from a terminal. What is the best fix?

Accepted Answer

Use absolute paths for all commands in the script.. Cron jobs run in a minimal environment with a restricted PATH (often just /usr/bin:/bin). When the script uses commands like 'tar' and 'gzip' without absolute paths, the shell cannot locate them. Using absolute paths (e.g., /bin/tar, /bin/gzip) ensures the script always finds the commands regardless of the environment.

Answer

Run the cron job as root.

Answer

Modify the script to source the user's .bashrc.

Answer

Add a PATH statement to the cron job definition.

Question 9

Which TWO commands can be used to list the contents of a tar archive without extracting it?

Accepted Answer

tar -tvf archive.tar. `tar -tvf archive.tar` lists the contents of a tar archive without extracting it. The `-t` flag tells tar to list the archive's table of contents, `-v` provides verbose output (showing file permissions, ownership, size, and timestamp), and `-f` specifies the archive file. This works for uncompressed tar archives.

Answer

tar --list archive.tar

Answer

tar -xjf archive.tar.bz2

Answer

tar -xvf archive.tar

Question 10

Which THREE commands can change the priority of an already running process?

Accepted Answer

top (press 'r'). The `top` interactive command allows you to change the priority (nice value) of a running process by pressing 'r' and entering the PID and new nice value. This directly modifies the process's scheduling priority without restarting it.

Answer

kill -STOP

Answer

nice

Question 11

Which TWO commands can display the current environment variables?

Accepted Answer

env. The `env` command (option C) is correct because it displays all current environment variables along with their values. It is a standard Unix/Linux command specifically designed for this purpose, and it is commonly used in scripting and troubleshooting to inspect the environment.

Answer

set

Answer

echo $HOME

Answer

export

Question 12

Refer to the exhibit. The file script.sh has permissions -rwxr-x--- and is owned by root with group 'developers'. A user named 'alice' is a member of the 'developers' group. Which command allows alice to execute the script without changing the file's group ownership?

Accepted Answer

usermod -aG developers alice. The question contains a logical twist: Alice is already a member of the developers group, and the file's group permission is r-x, so she already has execute permission. Therefore, no command is needed to allow execution. However, among the given choices, `usermod -aG developers alice` is the only command that does not alter the file itself (it merely reaffirms her group membership without changing the file's permissions or ownership). The other options modify the file, which is unnecessary and violates the requirement to not change the file's group ownership (or the file in any way). Thus, while redundant, option A is the best answer according to the question's constraints.

Answer

chmod o+x script.sh

Answer

chmod u+x script.sh

Answer

chown alice script.sh

Question 13

Refer to the exhibit. The output of 'ps aux' shows a process named 'process_hog' with PID 1234 consuming 99.5% CPU. The process is stuck in an infinite loop and does not respond to SIGTERM. Which signal should be used to forcefully terminate it?

Accepted Answer

kill -9 1234. SIGKILL (signal 9) cannot be caught, blocked, or ignored by a process, making it the only reliable way to terminate a process that is stuck in an infinite loop and unresponsive to SIGTERM. Since the process does not respond to SIGTERM (signal 15), a forceful kill with kill -9 is necessary.

Answer

kill -2 1234

Answer

kill -15 1234

Answer

kill -19 1234

Question 14

Refer to the exhibit. The /var partition is 100% full. Which command can be used to find the largest files in /var/log to free up space?

Accepted Answer

du -ah /var/log | sort -rh | head. It uses `du -ah` to list all files and directories in /var/log with human-readable sizes, pipes the output to `sort -rh` to sort them in reverse numerical order (largest first), and then uses `head` to display only the top entries. This combination efficiently identifies the largest files consuming space, allowing the administrator to target specific files for cleanup.

Answer

ls -lS /var/log

Answer

find /var/log -size +100M

Answer

df -h /var/log

Question 15

A system administrator needs to find all files in /var/log that have been modified in the last 24 hours. Which command accomplishes this?

Accepted Answer

find /var/log -mtime -1. `find /var/log -mtime -1` finds files modified less than 1 day ago (i.e., within the last 24 hours). The `-mtime` option with a negative number (`-1`) matches files whose content was modified less than n*24 hours ago, which is exactly what the question requires.

Answer

find /var/log -mtime 0

Answer

find /var/log -newer /var/log/syslog

Answer

find /var/log -mtime 1