CompTIA XK0-005 - CompTIA Linux+ Exam

The su command is used to switch to another user account on Linux systems. The - option makes the shell a login shell, which means that it will read the profile and environment variables of the target user. Without this option, the shell will retain the environment variables of the original user. This can cause confusion when issuing commands that depend on these variables, such as ls, which uses the $HOME variable to determine the home directory. Therefore, Ann should have issued su - Joe to list Joe’s files instead of her own. References: [How to Use su Command in Linux with Examples]

The docker build command is used to build an image from a Dockerfile and a context1. The Dockerfile is a text file that contains the instructions for creating the image, and the context is a set of files that can be used in the image creation process1. The file that the developer received is an example of a Dockerfile.

The -t option is used to specify a name and an optional tag for the image1. The name and tag are separated by a colon (:), and the tag is usually used to indicate the version of the image2. For example, -t myimage:1.0 means that the image will be named myimage and tagged as 1.0.

The last argument of the docker build command is the path to the context, which can be a local directory or a URL1. The dot (.) means that the current working directory is the context2. Therefore, docker build -t myimage:1.0 . means that the image will be built from the Dockerfile and the files in the current working directory, and it will be named myimage and tagged as 1.0.

The git checkout -b staging command creates a new branch called staging and switches to it. This is useful when you want to create a new branch locally and begin working on it. The -b flag is used to create the branch if it doesn’t exist.

The correct way to open a port for SSH using firewalld is:

bash

firewalld-cmd --permanent --add-port=22/tcp

This command allows TCP traffic on port 22 (the default port for SSH).

Option B only displays saved rules and doesn’t open the port.

Option C contains incorrect syntax: --dport sshd is invalid (sshd is a daemon, not a port number).

Option D removes the SSH service from the firewall, which is the opposite of the requirement.

The chgrp command is used to change the group ownership of files and directories. By using this command, the administrator can assign the files in the newly created directory to the human resources group, which will allow the users in that group to access them. The other commands are not relevant for this task. For example:

chattr is used to change the file attributes, such as making them immutable or append-only1.

chage is used to change the password expiration information for a user account2.

chcon is used to change the security context of files and directories, which is related to SELinux3.

To enable IP forwarding, the kernel parameter net.ipv4.ip_forward must be set to 1. This is done by appending net.ipv4.ip_forward=1 to /etc/sysctl.conf and applying the changes using sysctl -p. This command ensures that the system can forward packets between different network interfaces.

The chmod command is used to change the permissions of files and directories on Linux systems. The g+s option sets the setgid bit on a directory, which means that all files and folders created inside that directory will inherit the group name of the parent directory. This command can help the developer ensure that all files and folders created inside the /GroupOODEV directory have the same group name as /GroupOODEV. References: [How to Use chmod Command in Linux with Examples]

The top command provides a real-time, dynamic view of system performance, showing CPU, memory usage, and running processes — essential for identifying performance bottlenecks.

jobs shows background jobs in a shell session.

renice is used to change process priority but doesn’t diagnose issues.

pkill terminates processes but doesn’t monitor performance.

A is correct syntax to bring up a network interface.

Incorrect Options:

B, C, D: Invalid or misused ip link subcommands.

RAID 1 mirrors data across two disks for redundancy.

RAID 0 uses striping with no redundancy.

RAID 5/6 use parity, not mirroring.