Full Access LPI 010-160 Tutorials

 The PATH environment variable is a special variable that contains a list of directories that the system searches when looking for a command to execute12. The purpose of the PATH variable is to make it easier and faster for users to run commands without having to type the full path to the executable file. For example, if you want to run the ls command, which is located in the /bin directory, you don’t have to type /bin/ls every time. You can just type ls, and the system will find the executable file in the /bin directory, which is one of the directories in the PATH variable. The PATH variable can be viewed with the echo command12:

$ echo $PATH

The PATH variable can also be modified by adding or removing directories, either temporarily or permanently, depending on the user’s needs12. For example, if you have acustom script or program in your home directory, and you want to run it from anywhere, you can add your home directory to the PATH variable with the export command12:

$ export PATH=$PATH:~/myprogram

This will append your home directory to the end of the PATH variable, and the system will search it last when looking for a command. To make this change permanent, you need to edit a configuration file, such as ~/.bashrc or ~/.profile, and add the export command there12.

References:

• How To View and Update the Linux PATH Environment Variable | DigitalOcean
• Linux path environment variable - Linux command line - LinuxConfig.org

The command pwd stands for “print working directory”. It will print the absolute path of the current working directory to the terminal. For example, if we are currently in the /home/user/directory, it will print out that exact path1. The pwd command is useful for finding out where we are in the file system hierarchy and for verifying the location of files and directories2.

The other options are not commands that show the absolute path to the current working directory. The who command shows the users who are currently logged in to the system3. The cd … command changes the current working directory to the parent directory of the current one2. The ls -l command lists the files and directories in the current working directory in a long format, which shows the permissions, ownership, size, date, and name of each file and directory2. The cd ~/home command changes the current working directory to the /home directory under the user’s home directory, which may or may not exist2. References:

• Linux Essentials Exam Objectives, Version 1.6, Topic 103.1, Weight 2
• Linux Essentials Certification Guide, Chapter 3, Page 51-52
• How to Get the current directory in Linux - howtouselinux
• How To Find The Absolute Path Of A File Or Directory In Linux - systranbox

The UID of the user root is always 0 on Linux systems. This is because the kernel uses the UID 0 to check for the superuser privileges and grant access to all system resources. The name of the user account with UID 0 is usually root, but it can be changed or have aliases. However, some applications may expect the name root and not work properly with a different name. The UID 0 is reserved for the root user and cannot be assigned to any other user. The UID 0 is stored in the /etc/passwd file along with other user information. References:

• Linux Essentials Topic 104: The Linux Operating System, section 104.4: Runlevels and Boot Targets.
• Linux Essentials Topic 106: Security and File Permissions, section 106.1: Basic security and identifying user types.
• Linux Essentials Topic 106: Security and File Permissions, section 106.2: Creating users and groups.

 In Linux, every file and directory is associated with an owner and a group. The owner is the user who created the file or directory, and the group is the group to which the owner belongs. Therefore, each file is owned by exactly one user and one group. This is true for option A. The other options are false for the following reasons:

• Option B: The owner of a file does not always have full permissions when accessing the file. The permissions are determined by the file mode, which can be changed by the owner or the root user. The file mode specifies the read, write, and execute permissions for the owner, the group, and others. The owner can have different permissions than the group or others.
• Option C: The user owning a file does not have to be a member of the file’s group. The owner can change the group ownership of the file to any group on the system, regardless of whether the owner belongs to that group or not. However, only the root user or a user with the CAP_CHOWN capability can change the group ownership to a group that the owner is not a member of.
• Option D: When a user is deleted, all files owned by the user do not disappear. The files remain on the system, but their owner is changed to an invalid user ID (UID). The files can still be accessed by the group or others, depending on the permissions. The files can also be reclaimed by the root user or a user with the CAP_CHOWN capability, who can change the owner to a valid user.
• Option E: The owner of a file can be changed once it is assigned to an owner. The owner can transfer the ownership to another user, or the root user or a user with the CAP_CHOWN capability can change the owner to any user on the system. The command to change the owner of a file is chown. References: 1: Chown Command in Linux (File Ownership) | Linuxize 2 3: Linux File Permissions and Ownership Explained with Examples 4 2: 3 Ways to Find File Owner in Linux - howtouselinux 1