LFCS Practice Test 2 — 25 Questions

Question 1

An administrator needs to schedule a cron job that runs a script every day at 3:00 AM, but the system is in a different time zone (UTC) than the administrator's local time (EST). The administrator wants the job to run at 3:00 AM local time regardless of system time zone changes. What is the best approach?

Accepted Answer

Use the CRON_TZ variable in the crontab file to specify EST and schedule at 3:00 AM. Option B is correct because the CRON_TZ variable, when set in a crontab file, allows you to specify a time zone for the cron daemon to interpret the schedule entries. This ensures the job runs at 3:00 AM EST regardless of the system's default time zone (UTC), and it persists even if the system time zone changes, as cron uses the variable for scheduling.

Answer

Change the system time zone to EST and set the cron job to run at 3:00 AM

Answer

Set the TZ environment variable in the crontab file before the job definition

Answer

Calculate the UTC equivalent (8:00 AM UTC) and schedule the job at that time

Question 2

An administrator is troubleshooting a server that runs a critical application. The server has 16 GB of RAM and 8 CPU cores. The administrator notices that the server becomes very slow during peak hours. Analysis of 'iostat -x 1' shows that the average wait time (await) for the main disk (sda) is consistently above 1000 ms, while the average service time (svctm) is around 5 ms. What is the most likely cause?

Accepted Answer

There is a large queue of I/O requests waiting to be serviced.. The 'await' value in iostat represents the average time (in milliseconds) for I/O requests to be serviced, including time spent waiting in the queue. With 'await' at 1000+ ms and 'svctm' at only 5 ms, the vast majority of the time is spent waiting, not being serviced. This indicates a large queue of pending I/O requests, which is the direct cause of the slowdown.

Answer

The CPU is overloaded, causing processes to wait for CPU time.

Answer

The system is using swap space heavily, causing disk I/O.

Answer

The disk is experiencing hardware errors.

Question 3

Which TWO of the following are correct statements about systemd journald configuration?

Accepted Answer

The 'MaxRetentionSec' directive sets the maximum time to retain journal entries.. Option A is correct because the 'MaxRetentionSec' directive in journald.conf specifies the maximum time (in seconds) that journal entries are retained before they are deleted. This is a time-based retention policy, distinct from size-based limits, and is used to automatically prune old log entries to manage disk usage.

Answer

The 'RuntimeMaxUse' directive applies to the journal stored in /var/log/journal.

Answer

The 'Compress' directive is set to 'no' by default.

Answer

The 'ForwardToSyslog' directive is set to 'yes' by default.

Question 4

Which TWO commands can be used to display the groups to which the current user belongs? (Select exactly two.)

Accepted Answer

id. The `id` command (option C) displays the current user's UID, GID, and all supplementary group memberships. When run without arguments, it shows the effective user and group IDs along with all groups the user belongs to, making it a direct and reliable way to list group membership.

Answer

cat /etc/group

Answer

groupmems -l

Answer

getent group

Question 5

A systems administrator needs to add a new user 'jdoe' with a home directory in /export/home, a UID of 1500, and an expiry date of 2025-12-31. Which command should they use?

Accepted Answer

useradd -u 1500 -d /export/home/jdoe -e 2025-12-31 jdoe. Option A is correct because the `useradd` command with `-u 1500` sets the UID, `-d /export/home/jdoe` explicitly specifies the home directory path (without creating it unless `-m` is also used), and `-e 2025-12-31` sets the account expiry date in YYYY-MM-DD format. This matches all requirements: UID 1500, home directory at /export/home/jdoe, and expiry on 2025-12-31.

Answer

useradd -u 1500 -d /export/home/jdoe -c 2025-12-31 jdoe

Answer

useradd -u 1500 -m -e 2025-12-31 jdoe

Answer

useradd -u 1500 -b /export/home -e 2025-12-31 jdoe

Question 6

An administrator needs to grant a user named 'john' the ability to switch to any other user without a password. Which TWO of the following steps are required to achieve this?

Accepted Answer

Add 'john' to the 'wheel' group and configure /etc/pam.d/su to use pam_wheel.so with the 'trust' option.. Option A is correct because adding 'john' to the 'wheel' group and configuring /etc/pam.d/su with pam_wheel.so and the 'trust' option allows members of the 'wheel' group to switch to any user via su without being prompted for a password. The 'trust' modifier in PAM bypasses the password authentication for users in the specified group, effectively granting passwordless su access.

Answer

Set the suid bit on /bin/su.

Answer

Run 'usermod -L john'.

Answer

Add 'john' to the 'root' group.

Question 7

An administrator wants to add user 'bob' to the supplementary group 'docker' without removing bob from any existing groups. Which command accomplishes this?

Accepted Answer

usermod -aG docker bob. Option B is correct because the `-a` (append) flag combined with `-G` (supplementary groups) ensures user 'bob' is added to the 'docker' group without removing him from any existing supplementary groups. Without `-a`, the `-G` flag replaces the user's current supplementary group list with the specified groups.

Answer

usermod -g docker bob

Answer

usermod -G docker bob

Answer

usermod -G docker bob

Question 8

A security policy requires that user 'svc_backup' have a password that never expires. Additionally, the account should be locked after 90 days of inactivity. Which set of commands achieves this?

Accepted Answer

chage -M 99999 -I 90 svc_backup. Option C is correct because `chage -M 99999` sets the maximum password age to 99999 days, effectively preventing the password from ever expiring (since 99999 days far exceeds any practical lifespan). The `-I 90` flag sets the inactivity period to 90 days, meaning the account will be locked after 90 days of no login activity. This combination satisfies both security policy requirements: a non-expiring password and automatic lockout after 90 days of inactivity.

Answer

chage -W 7 -I 90 svc_backup

Answer

chage -E 2025-01-01 -I 90 svc_backup

Answer

chage -M 90 -I 90 svc_backup

Question 9

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. Option D is correct because `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 10

A DevOps engineer wants to measure how long a specific command takes to execute. Which command should be used?

Accepted Answer

time. Option D is correct because the `time` command is specifically designed to measure the execution duration of a command, reporting real time, user CPU time, and system CPU time. It wraps the target command and tracks the elapsed wall-clock time and resource usage, making it the precise tool for benchmarking command performance.

Answer

date

Answer

uptime

Answer

wall

Question 11

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

Accepted Answer

top (press 'r'). Option B is correct because 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 12

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 13

A DevOps engineer wants to list all running processes sorted by memory usage in descending order. Which command should be used?

Accepted Answer

ps aux --sort=-%mem. Option A is correct because `ps aux` lists all running processes, and `--sort=-%mem` sorts them by memory usage in descending order (the minus sign indicates descending). This is the standard way to identify memory-heavy processes for troubleshooting or resource monitoring.

Answer

ps aux --sort=%mem

Answer

ps aux --sort=+mem

Answer

ps aux --sort=-%cpu

Question 14

A user is unable to write to a file. The output of 'ls -l file' shows '-r--r--r--'. Which command will grant write permission to the owner?

Accepted Answer

chmod u+w file. The file's permissions are '-r--r--r--', meaning the owner has only read permission. The 'chmod u+w file' command adds write permission for the owner (u) because 'u' refers to the user/owner. This directly addresses the owner's lack of write access.

Answer

chmod o+w file

Answer

chmod a+w file

Answer

chmod g+w file

Question 15

An administrator needs to find the process ID of the cron daemon. Which combination of commands is most effective?

Accepted Answer

pidof cron. Option C is correct because `pidof cron` directly returns the numeric process ID(s) of the cron daemon by searching the process name in the `/proc` filesystem. It is the most straightforward command for this specific task, as it outputs only the PID without additional formatting or filtering.

Answer

top -p $(pgrep cron)

Answer

pgrep cron

Answer

ps -C cron -o pid=

Question 16

An administrator wants to terminate a process with PID 1234 and all its child processes. Which command should be used?

Accepted Answer

kill -9 -1234. Option B is correct because the `kill` command with a negative PID (e.g., `kill -9 -1234`) sends the signal to the process group identified by the absolute value of the PID. Since process group IDs typically equal the PID of the group leader, using `-1234` targets the entire process group, terminating PID 1234 and all its child processes. The `-9` (SIGKILL) ensures immediate termination without cleanup.

Answer

pkill -P 1234

Answer

kill -15 1234

Answer

kill -9 1234

Question 17

A user reports that they cannot run a script because it says 'Permission denied'. The script is owned by root and has permissions -rw-r--r--. Which command would allow the user to execute the script?

Accepted Answer

chmod +x script. The script has permissions `-rw-r--r--`, meaning the owner (root) has read/write, but no execute bit is set for any user. Option B (`chmod +x script`) adds the execute permission for all users (owner, group, others), which allows the user to run the script. Without the execute bit, the kernel will refuse to execve() the file, returning EACCES.

Answer

chmod u+s script

Answer

chmod -w script

Answer

chown user:user script

Question 18

A user 'alice' cannot log in via SSH. The administrator checks /etc/passwd and sees: alice:x:1002:1002::/home/alice:/sbin/nologin. Which command should be used to allow alice to log in with a bash shell?

Accepted Answer

usermod -s /bin/bash alice. Option C is correct because the /sbin/nologin shell in the /etc/passwd entry prevents alice from logging in via SSH. The usermod -s /bin/bash alice command changes alice's login shell to /bin/bash, allowing interactive SSH sessions. This directly addresses the shell restriction without altering other account properties.

Answer

usermod -d /home/alice alice

Answer

usermod -u 1002 alice

Answer

useradd -m -s /bin/bash alice

Question 19

A system administrator monitors a server that periodically becomes unresponsive for a few seconds. Investigation reveals that the kernel OOM killer is being invoked, but standard memory usage monitoring tools like 'free' and 'top' show less than 50% memory usage. The server runs a web server and a database. Which of the following is the most likely cause and diagnostic step?

Accepted Answer

The kernel is using a large amount of memory for slab caches. Use 'slabtop' to examine kernel memory allocations.. Option D is correct because the kernel OOM killer can be triggered by high slab cache usage, which is memory allocated for kernel data structures like inode and dentry caches. Standard tools like 'free' and 'top' may show low overall memory usage because they report only user-space memory, while slab caches are accounted separately. Using 'slabtop' allows the administrator to identify which kernel slab caches are consuming excessive memory, often due to a large number of small files or heavy filesystem metadata operations.

Answer

The server is experiencing a fork bomb. Use 'ps -ef | wc -l' to count processes.

Answer

The database is using swap space excessively. Use 'swapon -s' to check swap usage.

Answer

The web server is leaking file descriptors. Use 'lsof -n' to check open files.

Question 20

Which THREE of the following are valid Linux filesystem types that can be used for root partitions on a modern Linux system?

Accepted Answer

XFS. XFS is a high-performance 64-bit journaling filesystem created by Silicon Graphics, now widely supported in the Linux kernel. It is a valid choice for root partitions on modern Linux systems, especially for large file and high-concurrency workloads, and is the default filesystem in Red Hat Enterprise Linux 7 and later.

Answer

NTFS

Answer

FAT32