CompTIA Linux+ Practice Test (XK0-006)

The initramfs (or initrd) image is a compressed archive that the bootloader loads into memory together with the kernel. The kernel unpacks it to create a temporary root filesystem that contains the drivers, modules, and early-boot scripts required to locate and mount the real root filesystem-whether it resides on LVM, RAID, encrypted storage, or over the network. Once the real root is mounted, control passes to the normal init system and the initramfs is discarded from RAM. It is therefore not a GRUB configuration file (that is grub.cfg), a compressed kernel image (that is vmlinuz), or a sector-map file generated by LILO (that is /boot/map).

The correct command is passwd -l temp_user. The -l option locks the specified user's password by prepending an exclamation mark (!) to the encrypted password hash in the /etc/shadow file. This action prevents the user from authenticating with their password. The -u option is used to unlock an account that was previously locked with -l. The -d option deletes the user's password, which is a different action from locking it. The -e option expires the user's password, forcing them to change it at the next login, but it does not lock the account.

KVM (Kernel-based Virtual Machine) is a virtualization module in the Linux kernel that allows the kernel to function as a hypervisor. It directly leverages hardware virtualization extensions for CPU and memory management. However, KVM itself does not handle the emulation of other hardware like storage controllers, network cards, or USB ports. For this functionality, KVM relies on a user-space program, most commonly QEMU. QEMU provides the hardware emulation, while KVM provides the acceleration for CPU and memory, making them a powerful combination for high-performance virtualization. libvirt is a management toolkit and API, VirtIO provides paravirtualized drivers for performance, and Xen is a separate hypervisor technology.

The correct answer is to thoroughly review the playbook for correctness and security, and then test it in a staging environment. AI-generated code, including Infrastructure as Code (IaC), can contain subtle errors, security vulnerabilities, or use deprecated modules. It is the administrator's responsibility to validate any code before deployment. A thorough manual review combined with testing in a safe, non-production environment that mimics the production setup is the most critical step to ensure the playbook is safe and effective. Running the playbook on a single production node is dangerous as it could still cause an outage or security issue. Checking syntax with a linter is a good step, but it is insufficient as it will not catch logical errors or security misconfigurations. Adding comments for attribution is good practice for documentation but does not address the operational risk of running unverified code.

The correct answer is Bridged networking. This mode connects a virtual machine's network interface directly to the physical network, making it appear as another physical device on the LAN. The VM will get its own IP address on the same subnet as the host and other physical devices, allowing direct two-way communication.

• NAT (Network Address Translation) mode is incorrect because it isolates the VM on a private network. While the VM can initiate outbound connections, external devices cannot directly access services on the VM without special configuration like port forwarding.
• Host-only (or isolated) mode is incorrect because it restricts network communication to only the host machine and other VMs on that same host. It does not allow access from other physical devices on the network.
• Routed mode is incorrect for this scenario because, while it allows two-way communication without NAT, it involves placing the VM on a separate subnet and requires additional static routing configuration on the physical network's router to direct traffic to the VM. The scenario specifies the VM should be on the same subnet.

The correct command is nohup ./long_backup.sh &. The nohup command makes the script ignore the SIGHUP (hangup) signal, which is sent to processes when the controlling terminal is closed. The & operator runs the command in the background, freeing up the terminal for other commands and allowing the user to log out.

• Running the script with only & (./long_backup.sh &) will start it in the background, but it will still terminate when the session ends and the SIGHUP signal is sent.
• The bg command is used to resume a stopped job in the background; it is not used to initiate a new process in this manner.
• The exec command replaces the current shell with the script's process. It does not run the script in the background and will not prevent it from terminating upon logout.

The correct answer is Telnet. The Telnet protocol, which traditionally uses TCP port 23, transmits all data, including usernames and passwords, in clear text. The scenario described, with plaintext credentials on port 23, is a classic indicator of an active Telnet service. The best practice is to disable Telnet and replace it with SSH (Secure Shell), which encrypts the entire communication session. SSH is the secure alternative for remote command-line access, protecting credentials and data from being intercepted. FTP is also an insecure protocol that transmits credentials in plaintext, but it is used for file transfers and typically operates on ports 20 and 21. SFTP is a secure file transfer protocol that runs over SSH and would not exhibit this vulnerability.

The virsh blockcommit sub-command copies data from the top of a backing-file chain down into a specified base image while the virtual machine is running. Using the options --active and --pivot performs a live commit of the overlay data into base.img and then switches (pivots) the guest to use the consolidated base image, so the overlay files are no longer needed.

• blockpull moves data in the opposite direction (from the backing file up into the active overlay), leaving the chain length unchanged.
• snapshot-revert changes the VM to a previous snapshot state rather than merging disk images.
• blockcopy creates a new copy of a block device but does not collapse an existing snapshot chain.

Therefore, the only command that both merges the overlays into the base image and pivots the running guest in one step is blockcommit with the --active and --pivot options.

The Boolean that specifically allows Apache (httpd_t) to initiate network connections only to database servers is httpd_can_network_connect_db. Enabling it with setsebool -P httpd_can_network_connect_db on (or 1) makes the change persistent across reboots and satisfies the application's need to reach MySQL or MariaDB without granting the broader access provided by httpd_can_network_connect. The other options are either unrelated to database traffic or are not valid SELinux Booleans, so they do not resolve the denial.

The correct command is virsh setmem db-server-01 4G --live. The virsh setmem command is used to change a virtual machine's current memory allocation. The --live flag is crucial as it applies the change to the running instance of the virtual machine. The new memory size cannot exceed the maximum memory configured for the VM. The virsh edit command modifies the persistent XML configuration, but changes do not take effect until the VM is restarted. The virsh setmaxmem command is used to alter the maximum possible memory a VM can have, which also typically requires a restart to apply. virsh memtune is used for setting memory performance tuning parameters, not for changing the primary memory allocation.

The correct key combination to initiate the search and replace function in the nano text editor is Ctrl+\. After pressing this combination, nano will prompt for the search term, and then the replacement term. The user will then be prompted to replace the first instance, all instances, or skip to the next. The other options are incorrect. Ctrl+W is used to search for text (Where is). Ctrl+O is used to save the file (Write Out). Ctrl+G is used to display the help menu (Get Help).

The correct command is target_dir=${BACKUP_DIR:-/var/backups}.

• The ${parameter:-word} expansion checks if the variable BACKUP_DIR is unset or null. If it is, the expansion returns the default value /var/backups. Importantly, it does not change the value of BACKUP_DIR itself.
• The ${parameter:=word} syntax would also use the default value, but it would also assign /var/backups back to the BACKUP_DIR variable if it was unset or null, which is not desired according to the scenario.
• The ${parameter:+word} syntax does the opposite of what is needed; it expands to the word only if the parameter is set and not null.
• The ${parameter:?word} syntax would cause the script to exit with an error message if BACKUP_DIR were unset or null, which is intended for error handling, not for providing a default value.

The correct command is docker-compose up. This command is an aggregate command that automates the process of building images (if they do not already exist), creating containers, networks, and volumes, and then starting all the defined services. The docker-compose build command only builds or rebuilds the service images but does not start them. The docker-compose start command only starts existing containers that were previously created and are in a stopped state; it does not create them. The docker-compose exec command is used to execute a command inside an already running container.

The IPvlan driver allows multiple container interfaces to share the host's physical interface MAC address while giving each container its own IP address on the subnet. This satisfies the switch's single-MAC restriction and provides layer-2 connectivity without NAT. Macvlan assigns a unique MAC to every container, so the switch would see many MAC addresses and block traffic. A user-defined bridge keeps one MAC but relies on NAT, preventing the containers from being directly reachable on the VLAN. Host networking shares the host's IP stack, leaving containers without individual IP addresses. Therefore, IPvlan is the only option that meets all stated requirements.

PEP 8 explicitly says to use four spaces per indentation level and warns that Python 3 forbids mixing tabs and spaces. Converting every indent to four ASCII spaces removes the mixed whitespace that triggers the TabError and matches the style guide. Switching to tabs alone might eliminate the runtime error, but it ignores PEP 8's preference for spaces. Changing line endings or adding the -tt option does not fix existing mixed indentation and therefore will not meet both goals.

Pressing Ctrl + c causes the terminal driver to deliver the SIGINT (interrupt) signal, number 2, to every process in the current foreground process group. Unless the process has installed a custom handler or masked the signal, the kernel's default disposition for SIGINT is to terminate the process. That is why the cp command aborted as soon as you pressed Ctrl + c and control returned to the shell. SIGTERM (15) is the default signal sent by the kill command, not by Ctrl + c; SIGQUIT (3) is generated by Ctrl+\ and would terminate the process while producing a core dump; SIGTSTP (20) is generated by Ctrl+z and suspends (stops) the process rather than terminating it.

The -n 15 (or --lines=15) option limits output to the first 15 lines. The -v/--verbose option forces head to print the header that includes the filename every time, regardless of how many files are supplied. Together they meet both conditions.

Using -q/--quiet hides headers, so that choice fails. The form that omits -v relies on head's default behaviour, which prints a header only when more than one file is processed, so it would not show the header when a single file is passed. The -c option measures bytes rather than lines, so it does not meet the 15-line requirement.

The correct command is sed -i 's/192.168.1.5/10.10.0.5/g' app.conf. Here is a breakdown of the command:

• sed is the stream editor command.
• The -i option stands for "in-place" and modifies the file directly.
• 's/old/new/g' is the substitution command.
  • s indicates the substitute command.
  • /192.168.1.5/ is the pattern to search for.
  • /10.10.0.5/ is the replacement string.
  • g is the global flag, which ensures all occurrences on each line are replaced, not just the first one. The command sed 's/192.168.1.5/10.10.0.5/g' app.conf is incorrect because it lacks the -i flag; it will only print the modified text to standard output and will not save the changes to the file. The command sed 's/192.168.1.5/10.10.0.5/g' app.conf > app.conf is incorrect and dangerous. The shell processes the redirection > by truncating the output file (app.conf) before the sed command runs. This results in sed reading an empty file and the original content being lost. The command sed -i 's/192.168.1.5/10.10.0.5/' app.conf is incorrect because it is missing the global g flag. It would only replace the first occurrence of the IP address on any given line.

Ubuntu's default /etc/sudoers file already contains a line that delegates full sudo privileges to members of the sudo group:

%sudo   ALL=(ALL:ALL) ALL

Because this rule is present out-of-the-box, adding a user to the sudo group is enough to let them run any command via sudo. The rule still requires the user to authenticate with their own password, so the privilege is not password-less.

The other statements are inaccurate:

• The sudo group is not mapped to UID 0 and does not bypass the password prompt.
• PAM does not automatically grant system-wide capabilities such as CAP_SYS_ADMIN just because a user is in a particular group.
• polkit rules are unrelated to classic sudo group elevation on headless or server installations and do not remap the group to a wheel role.

The correct command is podman-compose down --volumes. The down command stops and removes containers and networks created by up. However, by default, it does not remove named volumes. The --volumes (or -v) flag must be added to also remove the named volumes defined in the compose.yaml file.

• podman-compose stop only stops the running containers; it does not remove them or any other resources like networks or volumes.
• podman-compose down on its own stops and removes containers and networks but leaves named volumes intact.
• podman-compose rm --force --volumes is incorrect because rm is used to remove already stopped containers, and it is not the primary command for tearing down a full environment. While it has a --volumes flag, it is for anonymous volumes, not the named volumes managed by the down command in a compose context. The down command is the more comprehensive and appropriate tool for this scenario.