EX200 Practice Test 23 — 15 Questions

Question 1

A developer runs the script shown in the exhibit and always sees 'Success' printed, even when the previous command fails. What is the most likely cause?

Accepted Answer

The $? variable captures the exit status of the [[ command, not the intended command. Option A is correct because $? is the exit status of the last command, which is the [[ command itself, not the command before the script. The [[ command returns 0 because the comparison is syntactically correct. Option B is wrong because $? is not the script's PID. Option C is wrong because [[ ]] does not return the negation. Option D is wrong because $? is set correctly but for the wrong command.

Answer

The [[ ]] syntax always evaluates to true

Answer

The $? variable is only set after external commands, not builtins

Answer

The $? variable always returns 0 in a conditional

Question 2

You maintain a script that performs a long-running task and must clean up temporary files if the script is interrupted. The script uses:

#!/bin/bash
tempfile=$(mktemp)
trap "rm -f $tempfile" EXIT
# long task
sleep 100

You notice that if the script receives SIGINT (Ctrl+C), the temporary file is not removed. Investigation shows that the trap on EXIT is not executed on SIGINT. Which modification should be made?

Accepted Answer

Add a trap for INT: `trap "rm -f $tempfile; exit" INT`.. Option B is correct because adding a separate trap for INT ensures cleanup on Ctrl+C. Option A (adding 'set -e') does not help. Option C using 'EXIT' with 0 is same as EXIT; not triggered on SIGINT. Option D putting the trap in a subshell would only affect the subshell.

Answer

Move the trap inside a subshell: (trap ... EXIT; long task).

Answer

Change `trap ... EXIT` to `trap ... 0`.

Answer

Add `set -e` at the beginning of the script.

Question 3

Which two commands can be used to view systemd journal entries for the sshd service?

Accepted Answer

journalctl -u sshd. Options A and B are correct. journalctl -u sshd and journalctl _SYSTEMD_UNIT=sshd.service both filter journal entries for sshd. Option C shows current status. Options D and E read traditional log files, not the journal.

Answer

systemctl status sshd

Answer

grep sshd /var/log/messages

Answer

tail -f /var/log/secure

Question 4

Which TWO methods correctly create a variable containing the number of regular files in the current directory (excluding . and ..)?

Accepted Answer

count=$(find . -maxdepth 1 -type f -printf '.' | wc -c). Option B uses find with -type f to count files, correctly handling filenames with spaces. Option D uses find with -printf to print a character per file, then wc -c counts characters. Option A includes directories. Option C uses ls -1A which shows all entries including directories. Option E uses stat but misses hidden files due to glob * not including dot files.

Answer

count=$(ls -1A | wc -l)

Answer

count=$(stat -c%F * | grep -c 'regular file')

Answer

count=$(ls -1 | wc -l)

Question 5

An ext4 filesystem on a logical volume has been extended with lvextend, but df -h still shows the old size. Which command must be run to make the filesystem aware of the new size?

Accepted Answer

resize2fs. Option D (resize2fs) is correct for ext4 filesystems. Option A (xfs_growfs) is for XFS. Option B (lvextend -r) would have performed the resize automatically if used initially. Option C (fsadm resize) is alternative but less common.

Answer

lvextend -r

Answer

fsadm resize

Answer

xfs_growfs

Question 6

Which three commands can be used to display overall memory usage information?

Accepted Answer

free. Options A, B, and C are correct. free shows memory summary. vmstat shows memory and more. top includes memory usage. ps aux shows per-process memory. uptime shows load averages only.

Answer

uptime

Answer

ps aux

Question 7

A system administrator needs to create a shell script that processes a list of hostnames stored in a file, one per line, and runs a command on each host. Which loop construct is most appropriate?

Accepted Answer

while read host; do ... done < hosts. Option B is correct because the 'while read' loop is the standard way to read a file line by line in shell scripts, handling each line as a separate variable. Option A is wrong because 'for' with '$(cat file)' can break on spaces. Option C is wrong because it uses 'seq' unnecessarily. Option D is wrong because 'until' is not suitable for this purpose.

Answer

for i in $(seq 1 $(wc -l < hosts)); do ... done

Answer

for host in $(cat hosts); do ... done

Answer

until read host; do ... done < hosts

Question 8

Which TWO of the following are valid ways to make a shell script executable?

Accepted Answer

chmod 755 script.sh. Option A and B are correct. 'chmod +x script.sh' adds execute permission, and 'chmod 755 script.sh' sets rwxr-xr-x. Option C is wrong because '. script.sh' sources the script but does not set execute permission. Option D is wrong because 'chmod u+x' is a subset of +x but still valid; however, the question asks for two, and A and B are the most common. Option E is wrong because 'bash script.sh' runs without execute bit.

Answer

bash script.sh

Answer

. script.sh

Answer

chmod u+x script.sh

Question 9

A script has a syntax error. Which command will help identify the line number of the error without executing the script?

Accepted Answer

bash -n script.sh. Option B is correct because 'bash -n script.sh' performs syntax checking only. Option A ('set -x') enables execution trace. Option C ('bash -v') prints lines as read. Option D shows the path of bash.

Answer

which bash

Answer

set -x

Answer

bash -v script.sh

Question 10

Which THREE of the following are common practices to improve the reliability of shell scripts?

Accepted Answer

Always quote variable expansions unless word splitting is intended. Options A, B, and C are correct. A: Using 'set -e' exits on error. B: Using 'set -u' treats unset variables as errors. C: Quoting variables prevents word splitting. Option D is wrong because using 'cat' inside loops is inefficient; use I/O redirection. Option E is wrong because using 'echo' for errors is not ideal; use '>&2' to redirect to stderr.

Answer

Use 'echo "Error"' for error messages without redirection

Answer

Use 'cat' to read files line by line in while loops

Question 11

A script needs to execute a command that might fail, but the script should continue. The administrator wants to capture the exit status for logging. Which code snippet correctly implements this?

Accepted Answer

./risky_command; rc=$?; echo $rc. Option C is correct because the exit status is captured immediately after the command. Option A is wrong because using 'set -e' would exit on failure. Option B is wrong because chaining with '&&' would skip the status capture if the command fails. Option D is wrong because the variable assignment and command execution are reversed.

Answer

set -e; ./risky_command; rc=$?; echo $rc

Answer

rc=$? ./risky_command; echo $rc

Answer

./risky_command && rc=$?; echo $rc

Question 12

Which systemctl command configures a service to start automatically at boot without starting it now?

Accepted Answer

systemctl enable service. Option B (systemctl enable service) creates the necessary symlinks to start at boot. Option A starts it immediately. Option C reenables. Option D sets default target.

Answer

systemctl set-default service

Answer

systemctl start service

Answer

systemctl reenable service

Question 13

Refer to the exhibit. Which command would free up the most space immediately?

Accepted Answer

journalctl --vacuum-size=500M. Option C (journalctl --vacuum-size=500M) reduces the size of systemd journal logs in /var/log/journal, which is a major contributor. Option A deletes all logs including necessary ones. Option B rotates logs but may not free space if old logs are not deleted. Option D clears package cache, not in /var/log.

Answer

yum clean all

Answer

rm -rf /var/log/*

Answer

logrotate -f /etc/logrotate.conf

Question 14

To mount an ext4 filesystem with the noatime option and remount read-only on errors, which file should be edited?

Accepted Answer

/etc/fstab. Option C (/etc/fstab) is the filesystem table that defines mount options. Option A (/etc/mtab) shows currently mounted filesystems. Option B is unrelated. Option D is a startup script.

Answer

/etc/mtab

Answer

/etc/sysconfig/network

Answer

/etc/rc.d/rc.local

Question 15

Based on the exhibit, what is the most likely cause of the failure?

Accepted Answer

Another process is already listening on port 22.. Option B is correct because the status message explicitly says 'Address already in use', indicating another process is listening on the same port (port 22). Option A is ambiguous; the port conflict is precise. Option C would produce a different error. Option D is incorrect because the service is enabled.

Answer

The SSH daemon is already running on another port.

Answer

The sshd configuration file has a syntax error.

Answer

The service is not enabled.

EX200 Practice Test 23 — 15 Questions

Exhibit

EX200 Practice Test 23 — 15 Questions

Exhibit