XK0-006 Practice Test 34 — 15 Questions

Question 1

A file has permissions -rwxr-x---. The administrator wants to give the group write permission using symbolic mode. Which command is correct?

Accepted Answer

chmod g+w file. The symbolic mode `g+w` adds write permission to the group owner of the file. The current permissions are `-rwxr-x---`, meaning the group has read and execute (`r-x`) but not write. The `g` stands for group, and `+w` adds write, resulting in `-rwxrwx---`.

Answer

chmod 775 file

Answer

chmod o+w file

Answer

chmod u+w file

Question 2

Refer to the exhibit. The system log is not updating. What is the cause?

Accepted Answer

The root filesystem is almost full, leaving no space for log growth.

Answer

The syslog file size exceeded 1GB and was rotated.

Answer

The syslog file permissions are incorrect.

Answer

rsyslogd was restarted and lost its configuration.

Question 3

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 4

A technician runs the command `sudo lvdisplay /dev/vg_root/lv_root` and sees the output in the exhibit. The server fails to mount the root filesystem during boot. Which of the following should the technician do first?

Accepted Answer

Run `lvchange -ay /dev/vg_root/lv_root` to activate the logical volume.. The `lvdisplay` output shows the logical volume is present but its 'LV Status' is likely 'NOT available' (not shown in the exhibit but implied by the boot failure). The root filesystem cannot mount because the logical volume is inactive. The first corrective step is to activate it with `lvchange -ay /dev/vg_root/lv_root`, which makes the LV accessible to the kernel for mounting.

Answer

Run `fsck /dev/vg_root/lv_root` to check the filesystem.

Answer

Run `vgchange -ay` to activate the volume group.

Answer

Run `mount /dev/vg_root/lv_root /mnt` to mount the volume.

Question 5

A system administrator is tuning a server for a high-performance computing workload and needs to disable NUMA (Non-Uniform Memory Access) at boot to improve memory access latency. Which kernel boot parameter should be added to the GRUB_CMDLINE_LINUX line in /etc/default/grub?

Accepted Answer

numa=off. The `numa=off` kernel boot parameter explicitly disables NUMA support in the Linux kernel, forcing memory to be treated as a single contiguous block (UMA). This eliminates the latency penalty of remote memory accesses, which is beneficial for high-performance computing workloads that require consistent, low-latency memory access across all CPUs.

Answer

maxcpus=1

Answer

acpi=off

Answer

noapic

Question 6

A Linux server with the IP address 192.168.1.100 is unable to communicate with other hosts on the same subnet 192.168.1.0/24. The administrator can ping the loopback address, but pinging 192.168.1.1 (the default gateway) fails. The output of `ip a` shows the eth0 interface has the correct IP and netmask. Which troubleshooting step should be performed next?

Accepted Answer

Check the routing table with ip route.. Since the server has the correct IP and netmask on eth0 but cannot ping the default gateway (192.168.1.1), the issue likely lies in the routing configuration. The `ip route` command displays the kernel routing table, including the default gateway entry; if the default route is missing or incorrect, traffic cannot reach the gateway. Checking the routing table is the logical next step before assuming physical or ARP-level problems.

Answer

Check the ARP cache with arp -a.

Answer

Replace the network cable.

Answer

Restart the network service.

Question 7

A Linux administrator is troubleshooting a server that intermittently becomes unresponsive. The administrator suspects a memory leak. Which command should be used to monitor memory usage over time and identify the consuming process?

Accepted Answer

top. The `top` command provides a real-time, dynamic view of system processes, including memory usage (RES, VIRT, %MEM) and can be sorted by memory consumption. It updates continuously, making it ideal for monitoring memory usage over time and identifying the specific process responsible for a suspected memory leak.

Answer

free -h

Answer

ss -tuln

Answer

df -h

Question 8

An application running under an AppArmor profile is being denied access to log files. The administrator wants to troubleshoot by allowing all actions and logging denials. Which command will switch the profile to complain mode?

Accepted Answer

aa-complain /path/to/profile. The `aa-complain` command places an AppArmor profile into complain mode, which allows all actions but logs denials to the system log. This is the correct tool for troubleshooting because it lets the administrator see what the application is trying to do without actually blocking it.

Answer

aa-enforce /path/to/profile

Answer

aa-disable /path/to/profile

Answer

aa-status

Question 9

A SysAdmin is investigating a server that has become unresponsive. The server was working fine, but after a recent update, it hangs during boot, showing 'A start job is running for /dev/mapper/rootvg-rootlv (xxs / no limit)'. This indicates a filesystem check is taking long. What is the most efficient way to skip the fsck and boot quickly?

Accepted Answer

Use the kernel parameter 'fsck.mode=skip'.. The kernel parameter 'fsck.mode=skip' instructs systemd to skip all filesystem checks during boot, allowing the server to bypass the stuck fsck job and start quickly. This is the most efficient method for a one-time skip without permanently altering configuration files.

Answer

At boot, press Ctrl+D to continue.

Answer

Boot into single-user mode and run fsck.

Answer

Edit /etc/fstab to set the sixth field to 0 for the root filesystem.

Question 10

A Linux engineer is troubleshooting a server that fails to boot. The server displays a message indicating 'Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)'. Which TWO actions should the engineer take to resolve this issue? (Choose TWO.)

Accepted Answer

Boot from a rescue disk and rebuild the initramfs with the necessary filesystem modules. The error 'Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)' indicates the kernel cannot locate or mount the root filesystem. Option B is correct because rebuilding the initramfs from a rescue disk ensures the necessary filesystem drivers (e.g., ext4, xfs) are included, which may have been missing or corrupted. Option D is correct because the root= parameter in the bootloader configuration (e.g., GRUB) tells the kernel which device/partition to mount as root; a typo or incorrect value (e.g., wrong UUID or device name) will cause this exact panic.

Answer

Reinstall GRUB to the Master Boot Record

Answer

Run fsck on the root partition to check for filesystem corruption

Answer

Disable SELinux by adding selinux=0 to the kernel command line

Question 11

Drag and drop the steps to troubleshoot a network connectivity issue using common commands in the correct order.

Accepted Answer

Verify IP configuration (ip addr), check default gateway (ip route), test DNS resolution (nslookup), ping remote host (ping). Troubleshooting network connectivity should follow a logical progression from local to remote: first verify your own IP address and subnet mask, then check the default gateway, then test DNS resolution, and finally test connectivity to a remote host. This systematic approach helps isolate the root cause efficiently.

Answer

Verify IP configuration (ip addr), test DNS resolution (nslookup), check default gateway (ip route), ping remote host (ping)

Answer

Ping remote host (ping), verify IP configuration (ip addr), check default gateway (ip route), test DNS resolution (nslookup)

Answer

Check default gateway (ip route), verify IP configuration (ip addr), test DNS resolution (nslookup), ping remote host (ping)

Question 12

Match each Linux boot component to its role.

Accepted Answer

GRUB: Loads the kernel and initramfs into memory. The Linux boot process: BIOS/UEFI loads GRUB → GRUB loads kernel & initramfs → kernel initializes hardware, mounts initramfs, loads drivers, then mounts real root and starts systemd → systemd manages services.

Answer

BIOS/UEFI: Initializes hardware and loads the kernel directly

Answer

systemd: Manages hardware initialization during boot

Question 13

Which THREE of the following are valid systemd unit types?

Accepted Answer

timer. A is correct because `timer` is a valid systemd unit type used to schedule and trigger other units (typically services) based on time events, similar to cron but integrated with systemd. Timers can be monotonic (relative to system events) or real-time (calendar-based), and they are defined in `.timer` files.

Answer

system

Answer

cron

Question 14

A Linux administrator is responsible for a critical application that runs as a systemd service on a server. The application occasionally hangs, and the administrator wants to automate the restart if the service becomes unresponsive. The administrator writes a Bash script that checks if the service is active and responsive by pinging a local health endpoint. If the health check fails three consecutive times, the script restarts the service. The script is intended to run every minute via a cron job. However, after implementing the cron job, the service is restarted even when it is functioning correctly, causing unnecessary downtime. The administrator reviews the script and finds the following logic:

#!/bin/bash
SERVICE="myapp"
COUNT_FILE="/tmp/${SERVICE}_failcount"
if curl -f http://localhost:8080/health; then
    echo 0 > "$COUNT_FILE"
else
    FAILS=$(cat "$COUNT_FILE" 2>/dev/null || echo 0)
    FAILS=$((FAILS + 1))
    echo "$FAILS" > "$COUNT_FILE"
    if [ "$FAILS" -ge 3 ]; then
        systemctl restart "$SERVICE"
        echo 0 > "$COUNT_FILE"
    fi
fi

What is the most likely cause of the false restarts?

Accepted Answer

Multiple instances of the script are running concurrently due to cron timing, causing a race condition on the count file.. The cron job runs the script every minute, but if the health check takes longer than a minute (e.g., due to network latency or a slow endpoint), multiple instances of the script can overlap. Each instance reads, increments, and writes the count file independently, causing a race condition where the fail count can be artificially inflated, leading to a false restart even when the service is healthy.

Answer

The count file is not being written because the script lacks write permissions to /tmp.

Answer

The script does not reset the count file after a successful health check.

Answer

The script does not handle the case where the count file does not exist on the first failure.

Question 15

A security analyst wants to identify all lines in a log file that contain either 'ERROR' or 'WARNING' and also contain 'timeout'. Which three commands can be used to achieve this? (Select THREE).

Accepted Answer

grep -E 'ERROR|WARNING' logfile | grep timeout. The correct commands are C, D, and E. Option C uses grep -E with alternation to first match lines containing 'ERROR' or 'WARNING', then pipes to another grep for 'timeout', ensuring both patterns appear in any order. Option D uses sed with alternation to print lines containing 'ERROR' or 'WARNING', then pipes to grep for 'timeout'. Option E uses awk with a condition requiring both patterns. Option B is incorrect because 'ERROR.*timeout|WARNING.*timeout' forces a specific order (e.g., 'timeout' must follow 'ERROR' or 'WARNING'), so it will miss lines where 'timeout' appears before the error/warning. Option A is wrong because -v inverts the match and the pattern lacks -E for alternation. Thus, only three options (C, D, E) correctly achieve the goal.

Answer

grep -v 'ERROR|WARNING' logfile | grep timeout

Answer

grep -E 'ERROR.*timeout|WARNING.*timeout' logfile