XK0-006 Practice Test 36 — 15 Questions

Question 1

Which directory in the Filesystem Hierarchy Standard (FHS) contains variable data such as logs and spool files?

Accepted Answer

/var. /var is the correct directory because the Filesystem Hierarchy Standard (FHS) designates /var for variable data files that are expected to change in size and content as the system runs, such as logs, spool files, and temporary files. This includes /var/log for system logs and /var/spool for print and mail queues. It is distinct from static data like binaries or configuration.

Answer

/opt

Answer

/etc

Answer

/tmp

Question 2

An administrator needs to permanently mount an ext4 filesystem on /dev/sdb1 to the /data directory. Which file must be edited to ensure the mount persists across reboots?

Accepted Answer

/etc/fstab. The /etc/fstab file is the system's static filesystem table, read by systemd or the init scripts during boot to mount filesystems automatically. To make a mount persistent, you add an entry specifying the device (/dev/sdb1), mount point (/data), filesystem type (ext4), and options (e.g., defaults). This ensures the kernel mounts the filesystem on every reboot without manual intervention.

Answer

/etc/sysconfig/network

Answer

/etc/default/grub

Answer

/etc/mtab

Question 3

An administrator wants to use Ansible to ensure that the `httpd` package is installed on all managed nodes. Which Ansible module should be used?

Accepted Answer

yum. The `yum` module is the correct choice because it is a dedicated Ansible module for managing packages on Red Hat-based systems using the YUM package manager. It ensures the `httpd` package is installed by setting the `state: present` parameter, and it handles idempotency by checking the package status before making changes.

Answer

copy

Answer

command

Answer

service

Question 4

A Linux administrator wants to prevent users from reusing their last five passwords. Which PAM module should be configured?

Accepted Answer

pam_pwhistory. The pam_pwhistory module is specifically designed to enforce password history policies by storing a user's previous passwords in a separate file (e.g., /etc/security/opasswd) and preventing reuse of those passwords. By configuring the 'remember' option in the PAM stack, the administrator can set the number of previous passwords that cannot be reused, such as 'remember=5' to block the last five passwords.

Answer

pam_faillock

Answer

pam_pwquality

Answer

pam_unix

Question 5

An application is being denied access to a file due to SELinux. Which command can be used to temporarily set the SELinux context of the file to match the expected type for the application?

Accepted Answer

chcon -t httpd_sys_content_t /var/www/html/index.html. The `chcon` command is used to temporarily change the SELinux context of a file without modifying the SELinux policy. By specifying `-t httpd_sys_content_t`, the file's type is set to the expected type for Apache (httpd) to access it, resolving the denial immediately. This change is not persistent across file system relabeling, making it ideal for temporary troubleshooting.

Answer

setenforce 0

Answer

restorecon -v /var/www/html/index.html

Answer

semanage fcontext -a -t httpd_sys_content_t /var/www/html

Question 6

In a Bash script, the administrator wants to capture the output of a command into a variable. Which syntax should be used?

Accepted Answer

$(command). Command substitution can be done with $(command) or backticks `command`. The latter is deprecated. $(( )) is for arithmetic expansion. $VAR is for variable expansion.

Answer

$VAR

Answer

$((command))

Answer

`command`

Question 7

A Linux server is experiencing high CPU usage. Which TWO commands can be used to identify which processes are consuming the most CPU? (Choose two.)

Accepted Answer

ps aux --sort=-%cpu. Option A, `ps aux --sort=-%cpu`, is correct because it lists all processes with their CPU utilization and sorts them in descending order by the %CPU column, immediately revealing the top CPU consumers. Option B, `top`, is correct because it provides a real-time, dynamically refreshing view of running processes ranked by CPU usage, allowing an administrator to identify which processes are consuming the most CPU. Option C, `iostat`, is incorrect because it reports CPU and I/O statistics per device rather than per-process CPU consumption. Option D, `vmstat`, is incorrect because it reports system-wide memory, paging, and CPU summary statistics, not individual process CPU usage. Option E, `free`, is incorrect because it only displays memory and swap usage, providing no per-process CPU information.

Answer

iostat

Answer

vmstat

Answer

free

Question 8

A service called 'myapp' fails to start automatically after a system reboot. The administrator wants to ensure the service starts at boot. Which systemctl command should be used?

Accepted Answer

systemctl enable myapp. The `systemctl enable myapp` command creates the necessary symlinks in the systemd unit configuration directories (typically `/etc/systemd/system/multi-user.target.wants/`) so that the `myapp` service is automatically started at boot. This is the correct approach because the question specifically asks to ensure the service starts after a reboot, not to start it immediately.

Answer

systemctl daemon-reload

Answer

systemctl start myapp

Answer

systemctl reenable myapp

Question 9

An administrator needs to generate a self-signed certificate and private key for an internal web server. Which OpenSSL command creates both in one step?

Accepted Answer

openssl req -x509 -newkey rsa:2048 -keyout key.pem -out cert.pem -days 365 -nodes. The `openssl req -x509 -newkey rsa:2048 -keyout key.pem -out cert.pem -days 365 -nodes` command generates a new RSA private key and a self-signed X.509 certificate in a single step. The `-x509` flag outputs a self-signed certificate instead of a CSR, `-newkey` creates the key pair, and `-nodes` prevents encryption of the private key, which is typical for an internal web server that must start without manual passphrase entry.

Answer

openssl ca -in req.pem -out cert.pem

Answer

openssl genrsa -out key.pem 2048 && openssl req -new -x509 -key key.pem -out cert.pem -days 365

Answer

openssl x509 -req -in req.pem -signkey key.pem -out cert.pem

Question 10

A user wants to view the contents of a text file one page at a time. Which two commands can be used? (Choose two.)

Accepted Answer

less. Both less (A) and more (E) are paging utilities that display a text file one screenful at a time and pause for the user to scroll, which directly matches the requirement. less is the more capable pager, supporting both forward and backward navigation plus searching, while more provides basic forward paging and is available on virtually all Unix-like systems. The other commands do not page output: cat (B) dumps the entire file to standard output at once, and tail (C) and head (D) only print the last or first lines (10 by default) respectively, so none of them let the user view the file page by page.

Answer

cat

Answer

tail

Answer

head

Question 11

An administrator configures /etc/ssh/sshd_config with the following settings: PermitRootLogin no, PasswordAuthentication no, AllowUsers alice bob, MaxAuthTries 2. After restarting sshd, which of the following is true?

Accepted Answer

User bob can log in using a public key.. PasswordAuthentication no disables password logins, so public key authentication is required. PermitRootLogin no prevents root login entirely. AllowUsers restricts to alice and bob only. MaxAuthTries 2 limits authentication attempts. So root cannot log in even with keys, and alice/bob must use keys.

Answer

User charlie can log in using a public key.

Answer

User alice can log in using a password.

Answer

Root can log in using a valid password.

Question 12

An administrator wants to find all files in the current directory tree that are larger than 100 MB and have the .log extension. Which find command will accomplish this?

Accepted Answer

find . -name '*.log' -size +100M. Find . -name '*.log' -size +100M. This command searches recursively from the current directory (.) for files with names matching '*.log' (-name '*.log') and with size greater than 100 MB (-size +100M). Option B is incorrect because the size syntax +100MB is wrong; the correct suffix is M for megabytes. Option C uses -size -100M which finds files smaller than 100 MB. Option D uses -type f (files only) but does not filter by .log extension, so it would include all files larger than 100 MB regardless of extension.

Answer

find . -name '*.log' -size +100MB

Answer

find . -name '*.log' -size -100M

Answer

find . -type f -size +100M

Question 13

An administrator needs to generate a self-signed certificate valid for 365 days with a 2048-bit RSA key. Which OpenSSL command correctly creates both the private key and certificate in one step?

Accepted Answer

openssl req -x509 -newkey rsa:2048 -keyout key.pem -out cert.pem -days 365 -nodes. The command 'openssl req -x509 -newkey rsa:2048 -keyout key.pem -out cert.pem -days 365 -nodes' generates a new 2048-bit RSA private key and a self-signed certificate in one step. The -x509 option outputs a self-signed certificate instead of a certificate request, and -nodes ensures the private key is not encrypted. This matches the requirement to create both the private key and certificate simultaneously.

Answer

openssl x509 -req -in req.pem -signkey key.pem -out cert.pem -days 365

Answer

openssl ca -newkey rsa:2048 -keyout key.pem -out cert.pem -days 365

Answer

openssl genrsa -out key.pem 2048 && openssl req -new -x509 -key key.pem -out cert.pem -days 365

Question 14

A security policy requires that users cannot reuse any of their last 5 passwords. Which PAM module and configuration directive enforces this?

Accepted Answer

pam_pwhistory with remember=5. The pam_pwhistory module records previous password hashes and enforces password reuse restrictions via the remember directive. Setting remember=5 prevents users from reusing any of their last five passwords, exactly matching the policy requirement.

Answer

pam_faillock with deny=5

Answer

pam_tally2 with deny=5

Answer

pam_pwquality with remember=5

Question 15

A system is running slowly and the administrator suspects a memory leak. Which THREE commands or tools can be used to analyze memory usage and identify processes consuming excessive memory? (Choose three.)

Accepted Answer

ps aux --sort=-%mem. Option B (ps aux --sort=-%mem) is correct because it lists all processes with their memory usage and sorts them in descending order by the %MEM column, directly revealing which processes consume the most memory. Option D (vmstat 1) is correct because it reports virtual memory statistics (swpd, free, buff, cache, si, so) every second, helping detect memory pressure and swapping indicative of a leak. Option E (free -h) is correct because it displays total, used, free, shared, buff/cache, and available memory in human-readable units, giving a quick overview of overall memory consumption. Option A (strace -p PID) is not appropriate here because strace traces system calls of a single process and does not summarize memory usage across processes. Option C (iostat -x) is incorrect because it reports extended disk I/O statistics, not memory usage.

Answer

strace -p PID

Answer

iostat -x