GNU and Unix Commands practice questions

A systems administrator needs to change the permissions of the file /home/user/script.sh so that the owner can read, write, and execute; the group can read and execute; and others have no access. Which command accomplishes this?

Trap 1: chmod 755 /home/user/script.sh

755 gives rwx for owner, r-x for group, and r-x for others, but others should have no access.

Trap 2: chmod 770 /home/user/script.sh

770 gives rwx for owner, rwx for group, and --- for others, but group has write access which is not required.

Trap 3: chmod 741 /home/user/script.sh

741 gives rwx for owner, r-- for group, and --x for others, which does not match.

A
chmod 755 /home/user/script.sh
Why wrong: 755 gives rwx for owner, r-x for group, and r-x for others, but others should have no access.
B
chmod 750 /home/user/script.sh
750 gives rwx for owner, r-x for group, and --- for others, matching the requirement.
C
chmod 770 /home/user/script.sh
Why wrong: 770 gives rwx for owner, rwx for group, and --- for others, but group has write access which is not required.
D
chmod 741 /home/user/script.sh
Why wrong: 741 gives rwx for owner, r-- for group, and --x for others, which does not match.

Question 2easymulti select

Which TWO commands can be used to view the contents of a compressed file named archive.tar.gz without extracting it to disk?

Trap 1: gzip -d archive.tar.gz

gzip -d decompresses, but does not list contents; it would produce archive.tar.

Trap 2: bunzip2 -c archive.tar.gz | tar -t

bunzip2 is for bzip2 compression; archive.tar.gz uses gzip.

Trap 3: gunzip -l archive.tar.gz

gunzip -l shows compression info, not the file list of the tar archive.

A
gzip -d archive.tar.gz
Why wrong: gzip -d decompresses, but does not list contents; it would produce archive.tar.
B
bunzip2 -c archive.tar.gz | tar -t
Why wrong: bunzip2 is for bzip2 compression; archive.tar.gz uses gzip.
C
tar -tzf archive.tar.gz
Correct: tar -t lists table of contents; -z handles gzip; -f specifies file.
D
gunzip -l archive.tar.gz
Why wrong: gunzip -l shows compression info, not the file list of the tar archive.
E
zcat archive.tar.gz | tar -t
Correct: zcat decompresses to stdout; pipe to tar -t lists contents.

Question 3hardmultiple choice

Refer to the exhibit. An administrator needs to edit /etc/example.conf to change setting1 to 'production' and add a new line 'setting2=value' after the include line. The file must be edited in place without creating a backup. Which command sequence achieves this?

Network Topology

Trap 1: sed -i 's/setting1=default/setting1=production/' /etc/example.conf;…

Second command uses i (insert before) instead of a (append after), so setting2 would be inserted before the include line, not after.

Trap 2: sed -i.bak 's/setting1=default/setting1=production/'…

Same as A, creates backup.

Trap 3: sed -i.bak 's/setting1=default/setting1=production/'…

Creates backups, not without backup.

A
sed -i 's/setting1=default/setting1=production/' /etc/example.conf; sed -i '/^include /a\nsetting2=value' /etc/example.conf
Correct: -i without argument edits in place; first command changes the setting; second appends after the include line.
B
sed -i 's/setting1=default/setting1=production/' /etc/example.conf; sed -i '/^include /i\nsetting2=value' /etc/example.conf
Why wrong: Second command uses i (insert before) instead of a (append after), so setting2 would be inserted before the include line, not after.
C
sed -i.bak 's/setting1=default/setting1=production/' /etc/example.conf; sed -i.bak '/^include /a\nsetting2=value' /etc/example.conf
Why wrong: Same as A, creates backup.
D
sed -i.bak 's/setting1=default/setting1=production/' /etc/example.conf; sed -i.bak '/^include /a\nsetting2=value' /etc/example.conf
Why wrong: Creates backups, not without backup.

Question 4mediummultiple choice

You are a Linux administrator for a company that runs a web server on a system with limited disk space. The web server logs are stored in /var/log/httpd/access_log and grow quickly. The operations team requires that the most recent logs be available for troubleshooting, but logs older than 7 days must be compressed to save space. You decide to implement log rotation using logrotate. The logrotate configuration file for httpd currently contains:

/var/log/httpd/*.log { daily rotate 7 compress delaycompress missingok notifempty sharedscripts postrotate /bin/systemctl reload httpd 2>/dev/null || true endscript

After applying this configuration, you notice that log files are being compressed immediately instead of after one rotation. What is the most likely cause and the correct step to fix this?

Trap 1: Remove the 'sharedscripts' directive to ensure the postrotate…

The sharedscripts directive does not affect compression timing; it only controls when the postrotate script runs.

Trap 2: Remove the 'delaycompress' directive to ensure compression occurs…

Removing delaycompress would cause all rotated logs to be compressed immediately, including the most recent, which contradicts the requirement to keep recent logs uncompressed.

Trap 3: Add the 'copytruncate' directive to avoid moving the log file,…

copytruncate does not affect compression timing; it only changes how the log file is rotated.

A
Remove the 'sharedscripts' directive to ensure the postrotate script runs for each log file individually.
Why wrong: The sharedscripts directive does not affect compression timing; it only controls when the postrotate script runs.
B
Change the rotation frequency to 'weekly' so that the most recent week's logs remain uncompressed and older logs are compressed.
With weekly rotation, the most recent rotated log (one week old) remains uncompressed due to delaycompress, while older logs are compressed, meeting the requirement of compressing logs older than 7 days.
C
Remove the 'delaycompress' directive to ensure compression occurs at each rotation.
Why wrong: Removing delaycompress would cause all rotated logs to be compressed immediately, including the most recent, which contradicts the requirement to keep recent logs uncompressed.
D
Add the 'copytruncate' directive to avoid moving the log file, allowing the web server to continue writing to the same file.
Why wrong: copytruncate does not affect compression timing; it only changes how the log file is rotated.

Question 5mediumdrag order

Arrange the steps to configure a static IP address on a Linux system using the command line.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Question 6mediumdrag order

Order the steps to recover a forgotten root password on a Linux system.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Question 7mediummatching

Read the full NAT/PAT explanation →

Match each Linux runlevel to its typical description.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts

Matches

Halt

Single-user mode

Multi-user with networking

Multi-user with GUI

Reboot

Question 8mediummatching

Match each device file naming pattern to its device type.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts

Matches

First SCSI/SATA disk

First NVMe SSD

First serial port (COM1)

First loopback device

First software RAID device

Question 9easymultiple choice

A systems administrator needs to find all files in /var/log that were modified in the last 24 hours and contain the word 'error'. Which command accomplishes this?

Trap 1: grep -r 'error' /var/log -mtime 0

The -mtime option is not valid for grep.

Trap 2: find /var/log -mmin 1440 -exec grep 'error' {}

Missing -l flag and broken syntax; also -mmin is not standard for 24 hours.

Trap 3: ls -l /var/log | grep error

ls does not search file contents.

A
grep -r 'error' /var/log -mtime 0
Why wrong: The -mtime option is not valid for grep.
B
find /var/log -mtime 0 -exec grep -l 'error' {} \;
Correctly uses find to filter by modification time and grep to search content.
C
find /var/log -mmin 1440 -exec grep 'error' {}
Why wrong: Missing -l flag and broken syntax; also -mmin is not standard for 24 hours.
D
ls -l /var/log | grep error
Why wrong: ls does not search file contents.

Question 10easymultiple choice

An administrator wants to change the ownership of a file to user 'jane' and group 'staff'. Which command should be used?

Trap 1: chown jane.staff file

Period is not the correct separator; use colon.

Trap 2: chgrp jane staff file

chgrp does not change user.

Trap 3: chown jane staff file

Missing colon between user and group.

A
chown jane.staff file
Why wrong: Period is not the correct separator; use colon.
B
chgrp jane staff file
Why wrong: chgrp does not change user.
C
chown jane:staff file
Correct syntax: user:group.
D
chown jane staff file
Why wrong: Missing colon between user and group.

Question 11mediummultiple choice

A developer is troubleshooting a shell script that uses the variable $HOME but it outputs nothing when the script runs. The script is executed with ./script.sh from an interactive shell. What is the most likely cause?

Trap 1: The script is run with sh instead of bash

HOME is usually set in sh as well.

Trap 2: The script is run with sudo

sudo may preserve HOME depending on configuration, but it's not the most likely cause.

Trap 3: The user has no home directory

All users typically have a home directory.

A
The script is run with sh instead of bash
Why wrong: HOME is usually set in sh as well.
B
The script is run with sudo
Why wrong: sudo may preserve HOME depending on configuration, but it's not the most likely cause.
C
The HOME variable is not exported
Variables must be exported to be available in child processes; interactive shells export HOME, but scripts invoked with ./ may not inherit if the parent shell is non-interactive.
D
The user has no home directory
Why wrong: All users typically have a home directory.

Question 12mediummultiple choice

An administrator needs to copy a directory hierarchy from one server to another over SSH, preserving permissions, ownership, and timestamps. Which command is most appropriate?

Trap 1: cp -a /source /mnt/remote

cp works locally, not over SSH without mounting.

Trap 2: scp -rp /source user@dest:/target

scp preserves timestamps but not ownership or ACLs.

Trap 3: rsync -avz /source user@dest:/target

rsync is good but requires rsync on both ends and may not preserve all metadata without -X and -A.

A
cp -a /source /mnt/remote
Why wrong: cp works locally, not over SSH without mounting.
B
tar cf - /source | ssh user@dest "tar xf - -C /target"
Preserves all metadata and works over SSH.
C
scp -rp /source user@dest:/target
Why wrong: scp preserves timestamps but not ownership or ACLs.
D
rsync -avz /source user@dest:/target
Why wrong: rsync is good but requires rsync on both ends and may not preserve all metadata without -X and -A.

Question 13hardmultiple choice

An administrator runs the command 'find / -name "*.conf" 2>/dev/null | head -n 10' and notices that the command returns very quickly. Which statement best describes what happened?

Trap 1: It lists 10 .conf files only from the current directory because the…

The path / means root, not current directory.

Trap 2: It lists all .conf files in the filesystem because head only…

head terminates find via SIGPIPE.

Trap 3: It lists only the first 10 .conf files found in the filesystem.

It lists the first 10 lines of output, but find may have found more; it stops early.

A
It scans the entire filesystem but stops after sending the first 10 lines to head due to a broken pipe.
Find continues until it tries to write after head closes, then stops.
B
It lists 10 .conf files only from the current directory because the path is /.
Why wrong: The path / means root, not current directory.
C
It lists all .conf files in the filesystem because head only affects output, not find.
Why wrong: head terminates find via SIGPIPE.
D
It lists only the first 10 .conf files found in the filesystem.
Why wrong: It lists the first 10 lines of output, but find may have found more; it stops early.

Read the full NAT/PAT explanation →

Question 14hardmultiple choice

A script uses 'set -e' and then executes 'grep pattern file'. If the pattern is not found, the script exits. Which of the following modifications would prevent the script from exiting while still allowing detection of the pattern's absence?

Trap 1: grep -q pattern file || true

The '|| true' makes the command always succeed, hiding the failure.

Trap 2: grep pattern file; exit_code=$?

The script would exit on grep failure before the assignment to exit_code.

Trap 3: grep pattern file | head -1

set -e still applies to the pipeline; if grep fails, the whole pipeline fails and exits.

A
grep -q pattern file || true
Why wrong: The '|| true' makes the command always succeed, hiding the failure.
B
set +e; grep pattern file; exit_code=$?; set -e
Temporarily disables exit-on-error, captures exit code, then re-enables.
C
grep pattern file; exit_code=$?
Why wrong: The script would exit on grep failure before the assignment to exit_code.
D
grep pattern file | head -1
Why wrong: set -e still applies to the pipeline; if grep fails, the whole pipeline fails and exits.

Question 15mediummultiple choice

Refer to the exhibit. Which file has a special permission that allows a user to execute the file with the privileges of the file owner?

Exhibit

-rwxr-xr-x 1 root root 12345 Jan 1 12:00 /usr/bin/myapp
-rwsr-xr-x 1 root root 23456 Jan 1 12:00 /usr/bin/su
-rw-rw-rw- 1 user1 user1 0 Jan 1 12:00 /tmp/shared

Trap 1: /usr/bin/myapp

No setuid bit; permissions are rwxr-xr-x.

Trap 2: /tmp/shared

No setuid bit; permissions are rw-rw-rw-.

Trap 3: None of the above

/usr/bin/su has setuid.

A
/usr/bin/myapp
Why wrong: No setuid bit; permissions are rwxr-xr-x.
B
/tmp/shared
Why wrong: No setuid bit; permissions are rw-rw-rw-.
C
/usr/bin/su
Has setuid bit (rws).
D
None of the above
Why wrong: /usr/bin/su has setuid.

Question 16hardmultiple choice

Refer to the exhibit. The process with PID 1234 is in state 'Z'. What is the most likely cause and appropriate action?

Exhibit

USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root         1  0.0  0.1  22564  4500 ?        Ss   Jan01   0:00 /sbin/init
user1      1234  0.0  0.0      0     0 ?        Z    Jan01   0:00 [defunct]
user1      1235  0.0  0.1  12345  2000 ?        S    Jan01   0:00 bash

Trap 1: The process is stopped; use kill -CONT to continue.

Stopped process shows state T, not Z.

Trap 2: The process is a daemon; it should be restarted.

Daemons typically show Ss or other states, not Z.

Trap 3: The process is sleeping; wait for it to become ready.

Sleeping processes show S or D.

A
The process is stopped; use kill -CONT to continue.
Why wrong: Stopped process shows state T, not Z.
B
The process is a daemon; it should be restarted.
Why wrong: Daemons typically show Ss or other states, not Z.
C
The process is sleeping; wait for it to become ready.
Why wrong: Sleeping processes show S or D.
D
The process is a zombie; the parent process must be killed or wait for it to be reaped.
Zombies require the parent to reap them; if parent is not waiting, it may need to be terminated.

Question 17easymultiple choice

Refer to the exhibit. Which file system is full and what is the likely consequence if the administrator does not take action?

Exhibit

Filesystem     1K-blocks    Used Available Use% Mounted on
/dev/sda1       10485760 9437184   1048576  90% /
/dev/sdb1       20971520 20971520       0 100% /var

Trap 1: Both are full; system will crash.

Only /var is full.

Trap 2: /dev/sda1 is full; system may become unstable.

/dev/sda1 is at 90%, not full.

Trap 3: Neither is full; available space is sufficient.

/dev/sdb1 has no available space.

A
Both are full; system will crash.
Why wrong: Only /var is full.
B
/dev/sda1 is full; system may become unstable.
Why wrong: /dev/sda1 is at 90%, not full.
C
Neither is full; available space is sufficient.
Why wrong: /dev/sdb1 has no available space.
D
/dev/sdb1 is full; applications writing to /var may fail.
The mount point /var is at 100% usage.

Question 18mediummulti select

Which TWO commands can be used to display the contents of a compressed file without decompressing it to disk? (Choose two.)

Trap 1: gzip -d file.gz

gzip -d decompresses to a file (removes .gz) unless output is redirected.

Trap 2: tar -xzf file.tar.gz

tar -x extracts the archive to disk.

Trap 3: uncompress file.Z

uncompress replaces the compressed file with the uncompressed version.

A
zcat file.gz
Equivalent to gunzip -c; outputs to stdout.
B
gzip -d file.gz
Why wrong: gzip -d decompresses to a file (removes .gz) unless output is redirected.
C
tar -xzf file.tar.gz
Why wrong: tar -x extracts the archive to disk.
D
bzcat file.bz2
Outputs bzip2-compressed file to stdout.
E
uncompress file.Z
Why wrong: uncompress replaces the compressed file with the uncompressed version.

Question 19hardmulti select

Which TWO of the following are valid methods to run a shell script named 'script.sh' using the bash shell, assuming the script has execute permission? (Choose two.)

Trap 1: sh script.sh

Runs with sh, not necessarily bash.

Trap 2: script.sh (if in PATH)

Same as ./script.sh but requires PATH; still uses shebang.

Trap 3: source script.sh

Sources the script into the current shell, not a separate process.

A
./script.sh
Executes the script using its shebang line, assumed to be bash.
B
sh script.sh
Why wrong: Runs with sh, not necessarily bash.
C
script.sh (if in PATH)
Why wrong: Same as ./script.sh but requires PATH; still uses shebang.
D
source script.sh
Why wrong: Sources the script into the current shell, not a separate process.
E
bash script.sh
Explicitly runs with bash.

Question 20easymulti select

Which THREE of the following are correct features of the 'grep' command? (Choose three.)

Trap 1: -l prints line numbers of matches

-l lists filenames with matches, not line numbers.

Trap 2: -r enables regular expression matching

-r enables recursive directory search; grep uses basic regex by default.

A
-i makes the search case-insensitive
Correct: --ignore-case.
B
-v inverts the match
Correct: --invert-match.
C
-c counts matching lines
Correct: --count.
D
-l prints line numbers of matches
Why wrong: -l lists filenames with matches, not line numbers.
E
-r enables regular expression matching
Why wrong: -r enables recursive directory search; grep uses basic regex by default.