XK0-006 Practice Test 37 — 15 Questions

Question 1

An administrator runs 'systemctl list-units' and sees that httpd.service is in a failed state. To quickly see the error message that caused the failure, which command should be used?

Accepted Answer

systemctl status httpd.service. The `systemctl status httpd.service` command displays the current state of the service, including the most recent log entries from the journal that show the error messages causing the failure. This is the quickest way to see the failure reason without filtering or additional options, as it directly outputs the relevant error lines from the service's unit.

Answer

systemctl show httpd.service -p ExecMainStatus

Answer

journalctl -p err -u httpd.service

Answer

systemd-analyze blame

Question 2

Which command displays the disk usage of files and directories in a human-readable format (e.g., KB, MB)?

Accepted Answer

du -h. The `du -h` command (disk usage with human-readable flag) recursively summarizes disk usage for files and directories, appending size suffixes like K, M, G for kilobytes, megabytes, and gigabytes. This directly matches the question's requirement to display disk usage in a human-readable format.

Answer

df -h

Answer

ls -lh

Answer

stat -h

Question 3

Refer to the exhibit. An API call returns HTTP 200 but an empty body. What is the most likely cause?

Accepted Answer

The request is missing required query parameters, such as pagination or filters.. The HTTP 200 status with an empty body (content-length: 0) indicates the server processed the request successfully but returned no data. This commonly occurs when the request lacks required parameters such as pagination, filters, or other query parameters that define the scope of the response. The server (nginx) is running and the SSL handshake succeeded, ruling out network or certificate issues. Therefore, the most likely cause is missing query parameters, as stated in Option A.

Answer

The server is experiencing a network timeout.

Answer

The SSL certificate is expired or invalid.

Answer

The API endpoint has been moved permanently (301).

Question 4

Based on the exhibit, what is the purpose of the audit rule?

Accepted Answer

Monitor all open syscalls by users with UID 1000 or higher.. The audit rule `-a always,exit -F arch=b64 -S open -F uid>=1000 -k monitor_open` uses the `uid>=1000` filter to match only system calls made by users with UID 1000 or higher. This is a common Linux auditd rule to track user-level activity while excluding system accounts (typically UIDs below 1000). Option C correctly identifies that the rule monitors all open syscalls by users with UID 1000 or higher.

Answer

Monitor open syscalls on a specific file.

Answer

Monitor all open syscalls by the root user.

Answer

Monitor all open syscalls except those by users with UID 1000 or higher.

Question 5

A system administrator needs to ensure that the Apache web server can read files in /var/www/html, which has the SELinux context httpd_sys_content_t. However, Apache is unable to access the files. What command should be used to apply the correct context to the directory and its contents?

Accepted Answer

restorecon -Rv /var/www/html. The directory /var/www/html already has the correct SELinux type (httpd_sys_content_t) as stated, but Apache cannot access the files. This suggests that the file contexts are not correctly applied or are mislabeled. The restorecon -Rv command resets the SELinux context of the directory and its contents to the default policy-defined context (httpd_sys_content_t), ensuring consistent labeling. This directly resolves the access issue without needing to define or change the context type.

Answer

chcon -R -t httpd_sys_content_t /var/www/html

Answer

fixfiles -R restore /var/www/html

Answer

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

Question 6

A server running nftables has a rule set that allows incoming SSH from the management network (192.168.1.0/24). An administrator needs to insert a rule to drop SSH from all other sources. Which nft command accomplishes this? Assume the input chain is 'input' and the table is 'inet filter'.

Accepted Answer

nft add rule inet filter input ip saddr != 192.168.1.0/24 tcp dport 22 drop. The correct command is A. The existing rule allows SSH from 192.168.1.0/24. To drop SSH from all other sources, we need a rule that matches packets with source IP address not in that subnet and destination port 22, and then drops them. The `add rule` subcommand appends the rule to the chain, which is appropriate because the allow rule for the management network should remain first. Using `ip saddr != 192.168.1.0/24` properly negates the source subnet. Option B drops SSH from any source (including the management network), which would block the allowed traffic. Option C replaces an existing rule by handle but does not specify the source condition. Option D accepts SSH from all sources, which is not desired. Therefore, A is correct.

Answer

nft insert rule inet filter input tcp dport 22 drop

Answer

nft replace rule inet filter input handle 1 tcp dport 22 drop

Answer

nft add rule inet filter input tcp dport 22 accept

Question 7

A database server is experiencing slow queries. The administrator wants to analyze system memory usage. Which command shows memory usage in megabytes and includes information about buffers and cache?

Accepted Answer

free -m. The 'free -m' command displays system memory usage in megabytes, explicitly showing separate columns for buffers and cache, which are critical for diagnosing slow queries caused by memory pressure. This makes it the correct choice for the administrator's need to analyze memory usage with buffer/cache details in MB.

Answer

top -b

Answer

cat /proc/meminfo

Answer

vmstat

Question 8

A Linux administrator needs to implement password complexity rules requiring at least one uppercase letter, one digit, and a minimum length of 10 characters. Which two PAM configuration entries would be used? (Choose TWO.)

Accepted Answer

password requisite pam_pwquality.so minlen=10 ucredit=1 dcredit=1. The `pam_pwquality.so` module enforces password complexity rules. The `minlen=10` parameter sets the minimum password length to 10 characters, `ucredit=1` requires at least one uppercase letter, and `dcredit=1` requires at least one digit. The `requisite` control ensures that if these checks fail, authentication is immediately denied. Option E is also correct because `enforce_for_root` applies the same complexity rules to the root user, which is often needed to fully enforce the policy. Options A, B, and D are incorrect: `pam_pwhistory.so` is for password history, not complexity; `pam_unix.so` does not enforce complexity; `pam_faillock.so` is an `auth` module for account lockout, not password strength.

Answer

password required pam_pwhistory.so use_authtok

Answer

password required pam_unix.so

Answer

auth required pam_faillock.so

Question 9

Which of the following Bash variable expansions will result in the string "Hello World"?

Accepted Answer

${GREETING:-'Hello World'} when GREETING is unset. ${var:-default} expands to the value of var if var is set and not null; otherwise, it expands to default. In option C, GREETING is unset, so ${GREETING:-'Hello World'} expands to 'Hello World'. Option A: ${GREETING:+World} with GREETING=Hello expands to 'World' because + uses alternate value when var is set. Option B: ${GREETING:-World} with GREETING=Hello expands to 'Hello' because var is set. Option D: ${GREETING:=World} with GREETING unset assigns 'World' to GREETING and expands to 'World', not 'Hello World'. Therefore, only option C yields 'Hello World'.

Answer

${GREETING:+World} when GREETING=Hello

Answer

${GREETING:-World} when GREETING=Hello

Answer

${GREETING:=World} when GREETING is unset

Question 10

A system administrator notices that the server is performing poorly. Running 'vmstat 1 5' shows high 'wa' values. Which subsystem is most likely experiencing a bottleneck?

Accepted Answer

Disk I/O. wa stands for I/O wait time, indicating the CPU is waiting for disk I/O. High wa suggests a disk bottleneck.

Answer

Memory

Answer

Network

Answer

CPU

Question 11

A technician needs to check the DNS A record for example.com using a specific DNS server at 8.8.8.8. Which command accomplishes this?

Accepted Answer

dig example.com @8.8.8.8 A. dig @8.8.8.8 example.com A queries the specified DNS server for the A record.

Answer

host -a example.com 8.8.8.8

Answer

dig -x 8.8.8.8 example.com

Answer

nslookup example.com 8.8.8.8

Question 12

A technician needs to check the kernel ring buffer for hardware errors detected during system boot. Which command should be used?

Accepted Answer

dmesg. dmesg displays kernel ring buffer messages, which include hardware detection and errors.

Answer

journalctl -k

Answer

lspci

Answer

cat /var/log/boot.log

Question 13

A Linux technician is troubleshooting a system that is experiencing high disk I/O wait times. Which TWO commands can be used to identify disk I/O performance issues? (Choose two.)

Accepted Answer

vmstat. iostat provides detailed disk I/O statistics including %util and await. dmesg may show disk errors but not performance stats. vmstat shows I/O wait (wa) column. free shows memory, lsof lists open files.

Answer

lsof

Answer

free -h

Answer

dmesg

Question 14

Which three are valid systemd unit types?

Accepted Answer

socket. B (socket), C (service), and D (timer) are all valid systemd unit types. A socket unit encapsulates a local IPC or network socket in the system for socket-based activation, a service unit describes a process controlled and supervised by systemd, and a timer unit provides a mechanism for triggering activation of other units based on time events. These are among the 12 standard systemd unit types defined in the systemd documentation.

Answer

process

Answer

job

Question 15

A Linux administrator needs to mount a new ext4 filesystem on /dev/sdb1 to /mnt/data. The administrator wants the filesystem to be mounted automatically at boot with noatime and with user ownership of files to be preserved (i.e., the filesystem should be owned by a specific user). Which line should be added to /etc/fstab?

Accepted Answer

/dev/sdb1 /mnt/data ext4 defaults,noatime 0 2. The 'uid=' mount option is not valid for ext4 filesystems; it is used for vfat or NTFS. For ext4, file ownership is stored on disk and preserved automatically. The correct answer is Option A: '/dev/sdb1 /mnt/data ext4 defaults,noatime 0 2'. It uses 'defaults' which includes ownership preservation, and 'noatime' meets the requirement. The value '2' for the pass field is appropriate for non-root filesystems. Option B's 'user' option allows any user to mount, not set ownership. Option D lacks 'noatime' and has an incorrect pass value of 0 for a filesystem that should be checked.

Answer

LABEL=DATA /mnt/data ext4 noatime,user 0 2

Answer

UUID=xxxx /mnt/data ext4 defaults,noatime,uid=1000 0 2

Answer

/dev/sdb1 /mnt/data ext4 rw,noatime 0 0