LFCS Practice Test 20 — 15 Questions

Question 1

A system administrator needs to ensure that a custom service named 'myapp.service' starts automatically after a reboot and also restarts automatically no matter how the service stops, even if it exits normally. Which two actions should the administrator take? (Choose two.)

Accepted Answer

Run 'systemctl enable myapp.service' to enable the service.. To start automatically on boot, the service must be enabled via 'systemctl enable'. To restart on any exit, 'Restart=always' must be set in the service file. 'Restart=on-failure' does not cover normal exits; 'After' and 'mask' are irrelevant.

Answer

Run 'systemctl mask myapp.service' to prevent manual stops.

Answer

Set 'Restart=on-failure' in the [Service] section of the service file.

Answer

Add 'After=network.target' to the [Unit] section of the service file.

Question 2

Refer to the exhibit. A Linux administrator sees that 'myapp.service' is in a failed state with exit status 1. To troubleshoot, which command should the administrator use to view the full error output that the service produced before exiting?

Accepted Answer

journalctl -u myapp.service. The journalctl command with the -u option shows all logs for the specified unit, including stdout/stderr captured by systemd. systemctl status only shows a brief log tail; restarting would remove the current state; reload does not affect failed units.

Answer

systemctl status myapp.service

Answer

systemctl reload myapp.service

Answer

systemctl restart myapp.service

Question 3

A system administrator is troubleshooting a server that fails to mount an XFS filesystem on /dev/sdb1 during boot. The filesystem was recently created. Which command should the administrator run to check the filesystem for corruption?

Accepted Answer

xfs_repair /dev/sdb1. Option B is correct because xfs_repair is the appropriate tool for repairing XFS filesystems. Option A is wrong because fsck.ext4 is for ext4 filesystems, not XFS. Option C is wrong because xfs_check is deprecated and not recommended; it has been replaced by xfs_repair. Option D is wrong because xfs_admin is used for tuning parameters, not checking for corruption.

Answer

fsck.ext4 /dev/sdb1

Answer

xfs_check /dev/sdb1

Answer

xfs_admin /dev/sdb1

Question 4

Which TWO commands should the administrator run to identify and fix the duplicate PV?

Accepted Answer

pvscan --cache. Options A and C are correct. Option A, pvscan --cache, rebuilds the LVM cache to update the view of available PVs and often removes duplicate entries. Option C, vgreduce --removemissing vg00, removes the missing PV from the volume group, which is appropriate after confirming the unknown PV is no longer available. Option B is wrong because vgimportclone is used to import a cloned volume group, not for removing duplicates. Option D is wrong because pvremove is destructive and would remove the PV metadata from /dev/sdc1, which might still be valid. Option E is wrong because adding a new PV does not resolve the duplicate issue.

Answer

vgextend vg00 /dev/sdd1

Answer

vgimportclone /dev/sdc1

Answer

pvremove /dev/sdc1

Question 5

A Linux administrator wants to restrict user 'alice' to only be able to use the system for non-interactive tasks (e.g., running cron jobs and receiving mail) but not allow her to log in via SSH or console. Which TWO actions would achieve this goal? (Choose two.)

Accepted Answer

Set alice's login shell to /sbin/nologin in /etc/passwd.. Options A and B are correct. Setting the shell to /sbin/nologin prevents interactive logins but cron and mail still work because they use /bin/sh independently. Adding to DenyUsers in sshd_config blocks SSH only. Option C does not block SSH key authentication. Option D gives root privileges instead of blocking. Option E blocks cron, which is not desired.

Answer

Lock alice's password with 'passwd -l alice'.

Answer

Change alice's UID to 0.

Answer

Add alice to /etc/cron.deny.

Question 6

A sysadmin set up a shared directory /data/project with group ownership project and permissions 2775 (rwxrwsr-x). Users in the project group can create files, but when they try to edit files created by other group members, they get permission denied. Which is the most likely cause?

Accepted Answer

The umask of users is set to 027, which prevents group write on new files.. Option A is correct because a umask of 027 would result in new files having permissions 640 (rw-r-----), lacking group write. Option B is wrong because 2775 includes the SGID bit. Option C is wrong because SGID still works with root ownership. Option D is wrong because the sticky bit affects deletion, not editing.

Answer

The directory is owned by root, so files inherit owner root, not the user's primary group.

Answer

The sticky bit interferes with group editing.

Answer

The SGID bit is not set; the directory must be chmod g+s to enforce group ownership inheritance.

Question 7

Refer to the exhibit. User alice attempts to create a file in /data/project but receives 'Permission denied'. User bob can create files successfully. What is the most likely reason?

Accepted Answer

Alice needs to run 'newgrp project' or log out and back in for her group membership to take effect.. Option C is correct. Although alice is a member of the project group, she was likely added after her current login session started; her supplementary groups are not updated until she logs out and back in or runs newgrp. Option A is false because groups shows she is in project. Option B is false because SGID does not affect write permission for project members. Option D is speculative and not indicated.

Answer

The directory's SGID bit requires primary group membership for write access.

Answer

Alice is not a member of the project group.

Answer

The directory has an ACL that denies write to user alice.

Question 8

A Linux administrator is troubleshooting a service that is running as the 'nobody' user but keeps failing because it cannot write to its log file. The log file is located at /var/log/app.log. Which TWO of the following methods will allow the service to write to the log file while maintaining security best practices?

Accepted Answer

Add an ACL entry for user nobody with write permission using setfacl.. Option B is correct because using setfacl to add an ACL entry for the 'nobody' user grants write permission without altering the file's ownership or group, preserving the principle of least privilege. ACLs provide fine-grained access control beyond traditional Unix permissions, allowing the service to write while other users and processes retain their existing access restrictions.

Answer

Delete /var/log/app.log and restart the service.

Answer

Change the group of /var/log/app.log to nogroup and set group write permission.

Answer

Change the permissions of /var/log/app.log to 777.

Question 9

A systems administrator is troubleshooting a server that runs a database application. The server has 64 GB of RAM and 16 CPU cores. The administrator notices that the system is using a significant amount of swap space even though there is plenty of free memory. The 'free -m' command shows: total memory = 65536, used = 50000, free = 15536, buffers/cache = 10000, swap total = 8192, swap used = 6000. Which of the following is the most likely cause?

Accepted Answer

The vm.swappiness value is set too high.. Option B is correct because a high vm.swappiness value (default 60) causes the kernel to aggressively swap out anonymous pages even when ample free memory exists. With 15 GB free and 10 GB in buffers/cache, the system should not be using 6 GB of swap unless swappiness is set too high, forcing premature swapping.

Answer

The vm.dirty_ratio and vm.dirty_background_ratio are set too high.

Answer

The database is configured to use huge pages, which are not swappable.

Answer

The vm.vfs_cache_pressure is set too low.

Question 10

To compress a file while preserving the original file, which command should be used?

Accepted Answer

gzip -k file.txt. Option D is correct because the `-k` (or `--keep`) flag in `gzip` instructs the utility to compress the file while retaining the original uncompressed file. By default, `gzip` replaces the original file with a compressed version (appending `.gz`), so `-k` is the explicit option to preserve the source file.

Answer

gzip file.txt

Answer

gzip -d file.txt.gz

Answer

gzip -1 file.txt

Question 11

Which TWO commands can be used to view the last 10 lines of a file and also follow new lines as they are written?

Accepted Answer

tail -f -n 10. Option A is correct because `tail -f -n 10` displays the last 10 lines of a file and then follows new lines as they are appended, using the `-f` (follow) flag. This is the standard way to monitor a log file in real time while initially showing the most recent 10 lines.

Answer

cat -n

Answer

tail -n 10

Answer

head -n 10

Question 12

Refer to the exhibit. The administrator receives alerts that the root filesystem is almost full. Which command could free up space by removing old log files?

Accepted Answer

find /var/log -name '*.log' -mtime +30 -delete. Option A is correct because the `find` command with `-name '*.log'` targets log files, `-mtime +30` selects files modified more than 30 days ago, and `-delete` removes them. This safely frees space by purging only old logs, preserving recent logs needed for troubleshooting.

Answer

truncate -s 0 /var/log/syslog

Answer

rm -rf /var/log/*

Answer

du -sh /var/log

Question 13

Which TWO commands can be used to mount a filesystem on /dev/sdb1 to /mnt/data?

Accepted Answer

mount /dev/sdb1 /mnt/data. Option B is correct because the standard syntax for the mount command is `mount [options] `, so `mount /dev/sdb1 /mnt/data` correctly specifies the device first and the target directory second. Option C is also correct because it explicitly specifies the filesystem type with `-t ext4`, which is a valid and common practice when mounting a filesystem, ensuring the kernel uses the correct driver.

Answer

mount /mnt/data /dev/sdb1

Answer

mount -o loop /dev/sdb1 /mnt/data

Answer

mount -t auto /dev/sdb1 /mnt/data -o loop

Question 14

A script needs to search for lines containing 'ERROR' in /var/log/syslog and count them. Which command pipeline achieves this?

Accepted Answer

grep ERROR /var/log/syslog | wc -l. Option C is correct because it uses `grep` to filter lines containing 'ERROR' from `/var/log/syslog` and pipes the output to `wc -l`, which counts the number of lines. This pipeline accurately counts the lines that match the pattern, which is the required task.

Answer

wc -l /var/log/syslog

Answer

grep ERROR /var/log/syslog | wc -c

Answer

grep -c ERROR /var/log/syslog

Question 15

A database administrator wants to compress a large directory of log files for archival. The administrator uses the command: tar -cvf logs.tar.gz logs/. The command completes successfully but the resulting archive is only 10 MB while the original directory is 100 MB. What is the most likely reason?

Accepted Answer

The 'z' flag was omitted, so the archive is not compressed.. Option C is correct because the command `tar -cvf logs.tar.gz logs/` does not include the `-z` flag, which is required to invoke gzip compression. Without `-z`, `tar` creates an uncompressed archive, and the `.gz` extension is misleading—the file is actually a plain tar archive. The resulting 10 MB size is simply the tarred version of the logs directory, not a compressed one, which explains why it is much smaller than the original 100 MB of uncompressed files.

Answer

The 'tar' command used relative paths and missed some files.

Answer

The logs directory contains many small files, causing high tar overhead.

Answer

The log files are already compressed individually.