LFCS Practice Test 37 — 15 Questions

Question 1

A system administrator is managing a RHEL 8 server that requires a static IP address on interface ens192. The administrator modifies /etc/sysconfig/network-scripts/ifcfg-ens192 to set BOOTPROTO=static, IPADDR=192.168.1.100, PREFIX=24, GATEWAY=192.168.1.1, and DNS1=8.8.8.8. After saving, the administrator runs 'systemctl restart NetworkManager'. The interface obtains the correct static IP and network connectivity works. However, after a reboot of the server, the interface fails to come up with the static IP and instead obtains an IP via DHCP from the local network. The administrator verifies that the DHCP server is active and that the physical connection is good. What is the most likely cause of the issue?

Accepted Answer

The ONBOOT parameter is set to no or missing in the configuration file.. The ONBOOT parameter controls whether the interface is activated at system boot. If set to 'no' or missing entirely, NetworkManager will not bring up the interface automatically after a reboot, causing it to fall back to DHCP if a DHCP client is active. Setting BOOTPROTO=static and IPADDR correctly only takes effect when ONBOOT=yes is present.

Answer

The kernel parameter nomodeset is set in /etc/default/grub.

Answer

The firewall is blocking the static IP assignment.

Answer

The network service is not enabled to start at boot.

Question 2

A user reports that a background process (PID 3456) is consuming 95% of CPU and causing system slowness. The process name is 'crypto-miner'. The administrator needs to immediately stop this process and ensure it does not restart. Which set of commands should the administrator execute?

Accepted Answer

kill -9 3456, then locate the cron job or systemd service that starts it, and disable/remove it.. Option A is correct because it addresses both immediate termination and persistence removal. The SIGKILL signal (kill -9) immediately terminates the process, and disabling the cron job or systemd service prevents automatic restart, which is critical for a malicious or unwanted process like 'crypto-miner'.

Answer

renice -n 19 -p 3456 and let it run with lower priority.

Answer

kill -9 3456 and then notify the user.

Answer

kill -15 3456 and hope it terminates.

Question 3

A company runs a web application stack consisting of a frontend web server (web.service) and a backend application server (app.service). The app.service uses Restart=on-failure to automatically restart if it crashes. The administrator wants the web.service to automatically restart whenever app.service restarts, so that the frontend remains in sync with the backend. Which directive should be added to the web.service unit file's [Unit] section to achieve this?

Accepted Answer

PartOf=app.service. Option B (PartOf=app.service) is correct because when app.service stops or restarts, PartOf causes systemd to stop or restart web.service as well, keeping the frontend in sync with the backend. Unlike BindsTo, PartOf does not create a strict dependency that would prevent app.service from starting independently, and it ensures the frontend follows the backend's state changes without requiring the backend to be fully operational for the frontend to start.

Answer

BindsTo=app.service

Answer

Requires=app.service

Answer

Wants=app.service

Question 4

A company runs a monitoring agent service (monitor.service) that must start after the network is fully up and the DNS resolver is ready. The service currently has the following dependencies in its unit file:

[Unit]
Description=Monitoring Agent
After=network.target
Wants=network.target

[Service]
ExecStart=/usr/bin/monitor

The service starts, but often fails to resolve hostnames because DNS is not yet available. Which change should be made to the unit file to ensure the service only starts after DNS is ready?

Accepted Answer

Add a dependency: After=nss-lookup.target. Option B is correct because `nss-lookup.target` is a synchronization point that indicates the hostname resolution subsystem (including DNS) is fully operational. By adding `After=nss-lookup.target`, the monitor service will not start until DNS resolution is available, solving the hostname resolution failures. The existing `Wants=network.target` is insufficient because `network.target` only signals that basic network interfaces are configured, not that DNS services are ready.

Answer

Replace After=network.target with After=network-online.target and add Requires=network-online.target

Answer

Add Before=network.target to delay the start

Answer

Set Type=idle in the [Service] section

Question 5

A large e-commerce platform runs on a database server that uses LVM thin provisioning. The thin pool is overcommitted at 200% (pool size 1TB, thin volumes total 2TB). Suddenly, the database reports write errors and performance degrades drastically. The administrator checks the system and finds that the thin pool is completely full. What is the immediate effect on the thin volumes, and what should the administrator do to restore normal operation without data loss?

Accepted Answer

The volumes become read-only; administrator must add more physical storage to the volume group and extend the thin pool.. Option A is correct because when an LVM thin pool is full, writes to thin volumes fail, and the volumes become read-only to prevent corruption. The solution is to add more physical storage to the volume group and extend the thin pool. Option B is incorrect because corruption does not occur immediately; data is safe if volumes go read-only. Option C describes behavior for snapshots, not primary volumes. Option D is false; thin pools do not auto-extend.

Answer

The volumes continue to operate but with severe slowdown; administrator must delete unnecessary snapshots.

Answer

The volumes become corrupted; administrator must restore from backup.

Answer

The volumes automatically extend the pool using metadata space; no action needed.

Question 6

A sysadmin is troubleshooting an issue where a software RAID1 array fails to assemble after a reboot. The array was created with mdadm using /dev/sdb1 and /dev/sdc1. The administrator checks /proc/mdstat but the array is not present. They attempt to assemble manually with mdadm --assemble /dev/md0 /dev/sdb1 /dev/sdc1, but it requires a repair. After repair, the array works. To prevent this from happening again, what should the administrator do?

Accepted Answer

Add an entry for the array in /etc/mdadm/mdadm.conf.. Option B is correct because adding an entry to /etc/mdadm/mdadm.conf (or /etc/mdadm.conf) with the array details allows the system to automatically assemble the array at boot. Option A is good practice but not mandatory for assembly. Options C and D are also good but B directly solves the missing auto-assembly.

Answer

Use UUIDs instead of device names in configuration.

Answer

Set the partition type to 'Linux RAID' on both partitions.

Answer

Rebuild the initramfs.

Question 7

You are managing a Linux server that hosts a critical application using a 500GB ext4 filesystem on an LVM logical volume. The application writes large log files that are rotated weekly. Recently, the system has been experiencing intermittent performance degradation and occasional 'Input/output error' messages when writing to the log directory. The disk (SSD) is relatively new, and SMART tests report no errors. The filesystem is not full, with 60% usage. You notice that the errors occur more frequently during peak write times. Which of the following is the most appropriate first step to diagnose and resolve the issue?

Accepted Answer

Unmount the filesystem and run 'e2fsck -f' to check and repair filesystem corruption.. Option C is correct: Running 'e2fsck -f /dev/vg/lv' will force a filesystem check and repair any inconsistencies that could cause I/O errors. Option A is wrong because SMART is already clean. Option B is wrong because mounting with noatime might help performance but won't fix errors. Option D is wrong because increasing LVM cache requires additional hardware and may not address filesystem corruption.

Answer

Add an LVM cache layer to improve write performance.

Answer

Replace the SSD immediately as it is likely failing despite SMART tests.

Answer

Mount the filesystem with the 'noatime' option to reduce write overhead.

Question 8

A system administrator is setting up a new backup server. The server has two 4TB disks /dev/sda and /dev/sdb. The administrator decides to create a RAID1 array and then an LVM volume group on top of the RAID device. After creating the RAID1 array /dev/md0, they create a physical volume, volume group named vg_backup, and a logical volume lv_data of size 2TB. Then they format with ext4 and mount at /backup. During testing, they realize that the backup data volume will likely exceed 2TB eventually. They want to expand the filesystem to use all available space in the RAID array. What is the correct procedure?

Accepted Answer

lvextend -l +100%FREE /dev/vg_backup/lv_data, resize2fs /dev/vg_backup/lv_data.. Option B is correct because lvextend -l +100%FREE extends the logical volume to use all free space in the volume group, and resize2fs can grow the ext4 filesystem online (without unmounting). Option A unmounts unnecessarily. Option C adds a new disk which is not needed. Option D creates a separate volume but does not consolidate space.

Answer

Unmount /backup, lvextend -l +100%FREE /dev/vg_backup/lv_data, resize2fs /dev/vg_backup/lv_data, mount /backup.

Answer

Create a new logical volume and mount it separately.

Answer

Add new disk to RAID array, then extend LVM.

Question 9

A server’s root filesystem on LVM is nearly full. The administrator has added a new 20GB disk and created a physical volume on it. They added the PV to the volume group containing root, then extended the root logical volume by 10GB. Next, they ran resize2fs on the mounted root filesystem. After the resize, the server continues to function. However, upon reboot, the system fails to boot and enters emergency mode. What is the most likely cause?

Accepted Answer

The initramfs needs to be regenerated to include the new disk.. Option B is correct because adding a new PV may change the order of LVM devices; the initramfs must include the LVM tools to mount root, and rebuilding it ensures the new PV is recognized. Option A is unlikely since resize2fs worked. Option C is not related to the disk addition. Option D fstab is unchanged and should still work.

Answer

The GRUB configuration is missing the new kernel.

Answer

The /etc/fstab entry for root is incorrect.

Answer

The filesystem was not resized correctly.

Question 10

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 11

You are a systems administrator for a company that runs a high-traffic web application on a Linux server with 32 GB of RAM and 8 CPU cores. The application uses Apache with mod_php and MySQL. Recently, the server has been experiencing intermittent slowdowns, especially during peak hours. Monitoring tools show that the CPU usage spikes to 100% for several minutes and then returns to normal. The 'top' command shows that the 'mysqld' process is often the top CPU consumer during these spikes. You notice that the MySQL slow query log contains many entries with long execution times. The database is heavily used by the web application for read-heavy workloads. After analyzing the situation, you suspect that the issue is related to MySQL configuration. Which of the following actions is most likely to resolve the performance issue?

Accepted Answer

Increase the MySQL query cache size (query_cache_size) to 256 MB.. Option C is correct because increasing the query cache size can significantly improve performance for read-heavy workloads with repeated identical queries, as it caches the result set of SELECT queries. The symptoms—CPU spikes from mysqld, many slow queries, and a read-heavy workload—indicate that the query cache is likely too small or disabled, causing MySQL to repeatedly execute expensive queries instead of serving cached results. A larger query cache reduces disk I/O and CPU usage for repeated queries, directly addressing the intermittent slowdowns.

Answer

Increase the maximum number of connections (max_connections) to 500.

Answer

Enable the MySQL slow query log and analyze the queries.

Answer

Increase the InnoDB buffer pool size to 20 GB.

Question 12

You are managing a multi-user Linux server used by a development team. The server has a shared directory /data/projects where each project has a subdirectory owned by a project lead. The requirement is that all members of the 'devteam' group need to be able to create files in any project subdirectory, but only the project lead (owner) should be able to delete files. Currently, members of devteam are unable to create files in /data/projects. You check permissions: /data/projects has drwxrwxr-x root:devteam. Each project subdirectory, e.g., /data/projects/proj1, has drwx------ lead1:devteam. The lead1 user is in devteam. What is the most likely reason that devteam members cannot create files in proj1, and what is the correct solution?

Accepted Answer

The proj1 directory lacks group write and execute permissions; use chmod g+rwx proj1 and chmod g+s proj1 to allow group members to create files and ensure new files inherit group.. Option D is correct because the project subdirectory /data/projects/proj1 has permissions drwx------ (700), which means only the owner (lead1) has read, write, and execute access. The devteam group lacks both write and execute permissions, preventing group members from creating files. The solution is to add group write and execute permissions (chmod g+rwx proj1) and set the setgid bit (chmod g+s proj1) so that new files inherit the group ownership, ensuring all devteam members can create files while only the owner can delete them.

Answer

The devteam group does not include all members; add each user to the devteam group.

Answer

The parent directory /data/projects lacks execute permission for devteam; add execute permission to /data/projects.

Answer

The sticky bit is not set; set the sticky bit on proj1 to allow only owners to delete files.

Question 13

A system administrator is managing a production web server running CentOS 7. The server hosts a critical application that depends on the 'httpd' package. Recently, the administrator attempted to install an updated version of httpd using 'yum update httpd', but the update failed with a dependency error: 'Error: Package: httpd-2.4.6-97.el7.centos.x86_64 requires libapr-1.so.0()(64bit)'. The administrator verifies that the apr package is installed (apr-1.5.2-6.el7.x86_64) and that the required library file exists at /usr/lib64/libapr-1.so.0. Despite this, yum continues to fail with the same error. After checking the yum repository configuration, the administrator notices that the base repository lists 'mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os' and the 'baseurl' is commented out. The system's /etc/yum.conf has 'keepcache=1'. What is the most likely cause of the dependency error, and which command should the administrator run to resolve it?

Accepted Answer

The repository metadata is stale; run 'yum clean all' then 'yum update'.. Option A is correct. The dependency error despite the library being present suggests stale repository metadata. yum clean all clears the cache and forces fresh metadata download, which often resolves such false positives. Option B is incorrect because the apr version provides the required library. Option C is similar to A but manual deletion is unnecessary. Option D bypasses dependency checks and risks breaking the system.

Answer

The yum cache is corrupted; delete /var/cache/yum manually and run 'yum makecache'.

Answer

The dependency is satisfied but yum's dependency resolver has a bug; use 'rpm -Uvh httpd.rpm --nodeps' to bypass dependency check.

Answer

The installed apr package is from a different version than what httpd expects; install a newer apr from a different repository.

Question 14

A DevOps engineer is writing a continuous integration pipeline that runs a script to deploy an application. The script is stored in a Git repository and is executed on a build server. The script works locally on the engineer's workstation, but when executed on the build server, it fails with '/bin/sh: line 12: somecommand: command not found'. The 'somecommand' is a standard Linux tool that is installed on the build server. The build server uses a minimal Docker container. Which of the following is the most likely cause and solution?

Accepted Answer

The PATH environment variable is not set correctly in the non-interactive shell. Use the full path to 'somecommand' or set PATH explicitly in the script.. The error 'command not found' despite the tool being installed indicates that the shell cannot locate the executable. In a non-interactive shell (like those used in CI/CD pipelines or minimal Docker containers), the PATH environment variable is often not set or is minimal. The fix is to either use the absolute path to the command or explicitly set PATH in the script to include the directory containing the command.

Answer

The script does not have execute permissions. Add 'chmod +x' before running the script.

Answer

The script requires root privileges. Use 'sudo' to run the script.

Answer

The script is using a different shell than the build server's default. Change the shebang to '#!/bin/sh'.

Question 15

Your company runs a critical database server that uses a 2TB XFS filesystem mounted at /data. The filesystem resides on an LVM logical volume (lv_data) within a volume group (vg_data) that spans four physical volumes (each 600GB SSD). You have been receiving low-space alerts: /data is at 95% capacity. After reviewing usage, you determine that the database will need an additional 500GB within the next month. The server has no additional physical disks available, but there is an unused 1TB SSD in inventory that you can install. However, the server is in production and cannot be rebooted. The system uses a 5.10 Linux kernel. Which of the following is the best approach to increase the available space for /data?

Accepted Answer

Install the new SSD, create a partition with fdisk, run pvcreate, vgextend vg_data, lvextend -L +500G /dev/vg_data/lv_data, and then run xfs_growfs /data.. Option C is correct because it follows the proper procedure to add a new physical disk to an existing LVM volume group, extend the logical volume, and then grow the XFS filesystem online without unmounting or rebooting. The `xfs_growfs` command is specifically designed to expand an XFS filesystem while it is mounted, which is essential for a production database server that cannot be rebooted.

Answer

Create a RAID 0 array with the existing SSDs and the new SSD using mdadm, then format with XFS and mount at a different mount point, then move data.

Answer

Shrink other logical volumes in vg_data that are not important to free up space, then extend lv_data.

Answer

Backup /data to an external drive, delete the logical volume, volume group, and physical volumes, then recreate everything including the new SSD to have a single large filesystem, then restore data.