XK0-006 Practice Test 38 — 15 Questions

Question 1

A Bash script contains the following function:

```bash
myfunc() {
  local result="$(( $1 + $2 ))"
  echo "$result"
}
```

If the script calls `myfunc 5 10`, what is the output?

Accepted Answer

15. The function uses arithmetic expansion $(( $1 + $2 )) with positional parameters 5 and 10, which evaluates to 15. The result is stored in a local variable and echoed to stdout, so calling myfunc 5 10 prints 15.

Answer

510

Answer

5+10

Answer

the function returns nothing

Question 2

A junior administrator needs to view the logs of a running container named 'webapp'. Which command should be used?

Accepted Answer

docker logs webapp. The `docker logs webapp` command retrieves the stdout and stderr output streams from the container's main process, which is the standard way to view logs for a running or stopped container. This is the correct approach because Docker captures these streams and stores them in a JSON file on the host, accessible via the `docker logs` command.

Answer

docker attach webapp

Answer

docker inspect webapp

Answer

docker stats webapp

Question 3

A system administrator wants to collect network performance statistics over time, including packet loss and latency, to diagnose intermittent connectivity issues. Which tool combines the functionality of ping and traceroute into a single continuous monitoring command?

Accepted Answer

mtr. mtr (My TraceRoute) continuously sends packets and displays real-time statistics including loss and latency for each hop, combining ping and traceroute.

Answer

tcpdump

Answer

ss

Answer

netstat

Question 4

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. In vmstat output, the 'wa' column reports the percentage of CPU time spent waiting for I/O operations to complete. High 'wa' values indicate that the CPU is idle but blocked waiting on disk (or other block device) I/O, which points directly to a disk I/O bottleneck. This is distinct from high 'us' or 'sy' (user/system CPU) or high 'si'/'so' (swap), which would indicate CPU or memory pressure respectively.

Answer

Memory

Answer

Network

Answer

CPU

Question 5

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. Option B (vmstat) is correct because it reports virtual memory statistics including the 'wa' (I/O wait) column in its CPU breakdown, which directly shows the percentage of time the CPU spent waiting on disk I/O, making it ideal for diagnosing high I/O wait times. Option C (iostat) is correct because it is specifically designed to report per-device and per-partition disk I/O statistics such as tps, kB_read/s, kB_wrtn/s, and %util, which pinpoint which block devices are saturated. Option A (lsof) lists open files and the processes using them, which can hint at file usage but does not measure disk I/O performance or wait times. Option D (free -h) only displays memory and swap usage in human-readable form, providing no direct disk I/O metrics. Option E (dmesg) shows kernel ring buffer messages, useful for hardware or driver errors, but it does not report ongoing disk I/O performance statistics.

Answer

lsof

Answer

free -h

Answer

dmesg

Question 6

A user cannot write to a directory that has permissions 755. The user is not the owner but belongs to the group. Which command would allow the user to write?

Accepted Answer

chmod 770 /directory. The directory currently has permissions 755, meaning the owner has rwx (7), the group has r-x (5), and others have r-x (5). Since the user belongs to the group but is not the owner, they need group write permission. The chmod 770 command sets the group permission to rwx (7), granting the user write access while preserving owner and group ownership semantics.

Answer

chmod 755 /directory

Answer

chmod 777 /directory

Answer

chmod 700 /directory

Question 7

A system administrator is investigating high disk I/O on a server. Which command can provide disk utilization statistics, including average wait time (await) and percentage of CPU time during which I/O requests were issued (%util)?

Accepted Answer

iostat -x 1. The `iostat` command reports disk I/O statistics including await and %util.

Answer

free -h

Answer

sar -b 1 5

Answer

vmstat 1 5

Question 8

An administrator wants to start a long-running script in the background so that it continues running even after logging out. Which command should be used?

Accepted Answer

nohup script.sh &. nohup (no hangup) makes the process immune to the SIGHUP signal that is sent to child processes when the controlling terminal closes on logout. Appending & backgrounds the job so the shell returns a prompt immediately. Combining both is required: nohup alone still runs in the foreground and blocks the terminal, while & alone leaves the process vulnerable to SIGHUP on logout.

Answer

script.sh &

Answer

nohup script.sh

Answer

bg script.sh

Question 9

A system administrator is troubleshooting a custom systemd service that fails to start. Which of the following commands should be used to diagnose the issue? (Choose two.)

Accepted Answer

systemctl status myservice. Option B, systemctl status myservice, is correct because it displays the current state of the unit, including whether it is active, failed, or inactive, along with the most recent log lines and the exit code, which directly helps diagnose why the service failed to start. Option E, journalctl -u myservice, is correct because it queries the systemd journal for all log messages associated with that specific unit, providing detailed error output, stack traces, or dependency failures needed to pinpoint the root cause. Option A, systemctl daemon-reload, only reloads unit file definitions after edits and does not diagnose a failing service. Option C, systemctl enable myservice, merely creates symlinks for automatic startup at boot and does not reveal why the service fails. Option D, systemctl list-units, gives a broad overview of loaded units but lacks the per-unit detail and logs required for troubleshooting a specific failed service.

Answer

systemctl daemon-reload

Answer

systemctl enable myservice

Answer

systemctl list-units

Question 10

A junior administrator reports that users cannot connect to a file server running Samba. The server is reachable via ping. Logs from the Samba service show: 'smbd: error while loading shared libraries: libgnutls.so.30: cannot open shared object file: No such file or directory'. The administrator confirms the package 'libgnutls' is installed. Which of the following is the most likely cause and solution?

Accepted Answer

The library path is not set; run ldconfig.. The error 'cannot open shared object file' indicates that the dynamic linker cannot find the libgnutls.so.30 library at runtime, even though the libgnutls package is installed. Running `ldconfig` updates the linker cache, which rebuilds the mapping of shared library names to their actual file paths, resolving the missing library reference for Samba.

Answer

The system libraries are out of sync; run apt-get update.

Answer

The Samba package is corrupted; reinstall Samba.

Answer

The Samba service is not running; restart it.

Question 11

A user wants to run a Docker container in detached mode, remove it automatically after it stops, and map host port 8080 to container port 80. Which command accomplishes this?

Accepted Answer

docker run -d --rm -p 8080:80 image. The `docker run` command is the correct choice because it combines container creation and startup in a single step. The `-d` flag runs the container in detached mode (in the background), `--rm` automatically removes the container filesystem when it exits, and `-p 8080:80` maps host port 8080 to container port 80. Together these flags satisfy all three requirements in one command.

Answer

docker run -it --rm -p 80:8080 image

Answer

docker create --rm -p 8080:80 image

Answer

docker start -d -p 8080:80 image

Question 12

A Linux administrator needs to view the last 10 lines of a log file named 'syslog'. Which command should be used?

Accepted Answer

tail -10 syslog. The 'tail' command outputs the last lines of a file; by default it shows 10 lines.

Answer

cat syslog

Answer

head -10 syslog

Answer

less syslog

Question 13

A container is running a web server on port 8080 internally, and the administrator wants to access it on the host on port 80. Which Docker run option accomplishes this?

Accepted Answer

-p 80:8080. The Docker -p flag maps a host port to a container port using the syntax -p HOST_PORT:CONTAINER_PORT. Since the container listens on 8080 internally and the administrator wants it reachable on host port 80, the correct mapping is -p 80:8080. This publishes the container's port 8080 to the host's port 80.

Answer

-P

Answer

-p 8080:80

Answer

--expose 8080

Question 14

A container is running and a technician needs to execute an interactive shell inside it. The container was started with 'docker run -d --name myapp myimage'. Which command will achieve this?

Accepted Answer

docker exec -it myapp /bin/bash. 'docker exec -it myapp /bin/bash' attaches a new interactive TTY session to the already-running container named myapp and launches /bin/bash inside it. The -i flag keeps STDIN open and -t allocates a pseudo-TTY, which is required for an interactive shell. Because the container is already running, exec is the correct tool rather than run.

Answer

docker attach myapp

Answer

docker run -it --name myapp myimage /bin/bash

Answer

docker logs -f myapp

Question 15

Which THREE are best practices for securing a Linux server? (Choose exactly three.)

Accepted Answer

Use a host-based firewall. Option A (Use a host-based firewall) is correct because tools like iptables/nftables or firewalld enforce least-privilege network access at the host level, blocking unneeded inbound ports even if a service is accidentally exposed. Option B (Keep software up to date) is correct because patching via the distribution's package manager (e.g., apt, dnf, yum) closes known CVEs in the kernel, libraries, and daemons that attackers actively exploit. Option D (Disable unnecessary services) is correct because every running daemon (e.g., telnet, rsh, unused web servers) expands the attack surface, so stopping and disabling them with systemctl reduces exploitable entry points. Option C is wrong because enabling root SSH login with a password invites brute-force and credential-stuffing attacks; best practice is PermitRootLogin no plus key-based authentication. Option E is wrong because umask 0777 removes all permissions from newly created files and directories, which is not a security best practice and would break normal system operation.

Answer

Enable root SSH login with password

Answer

Set default umask to 0777