LPI Linux Essentials 010-160 LPI Study Notes

The zip command is used to create compressed archive files that can contain one or more files or directories. The zip command takes the name of the archive file as the first argument, followed by the names of the files or directories to be included in the archive. You can also use wildcards to match multiple files or directories with a common pattern. For example, the command zip poems.zip *.txt will create the ZIP archive poems.zip containing all files in the current directory whose names end in .txt. The other commands are either invalid or do not perform the desired operation. The command zip *.txt > poems.zip will try to create an archive for each file ending in .txt and redirect the output to poems.zip, which is not a valid archive file. The command zcat *.txt poems.zip will try to decompress and concatenate the contents of the files ending in .txt and poems.zip, which is not a valid ZIP file. The command zip cfz poems.zip *.txt will fail because the options c, f, and z are not valid for the zip command. The command cat *.txt | zip poems.zip will try to read the contents of the files ending in .txt from the standard input and create an archive named poems.zip, but this will not preserve the file names or attributes of the original files. References:

• Linux Essentials - Linux Professional Institute (LPI), section 3.1.1
• 3.1 Archiving Files on the Command Line - Linux Professional Institute Certification Programs, slide

 Linux hardware drivers are software components that enable the Linux kernel to communicate with various devices, such as keyboards, mice, printers, scanners, network cards, etc. Drivers are either compiled into the Linux kernel or are loaded as kernel modules. Kernel modules are pieces of code that can be loaded and unloaded into the kernelon demand. They extend the functionality of the kernel without requiring to rebuild or reboot the system. Drivers that are compiled into the kernel are always available, but they increase the size and complexity of the kernel. Drivers that are loaded as kernel modules are only available when needed, but they require a matching version of the kernel and the module. Linux supports a large number of hardware devices, thanks to the efforts of the open source community and some vendors who provide drivers for their products. However, some devices may not have a driver available for Linux, or may require a proprietary driver that is not included in the Linux distribution. In such cases, the user may need to install the driver manually from the vendor’s website or from a third-party repository. References:

• Linux Essentials - Linux Professional Institute (LPI), section 2.2.1
• LPI Linux Essentials Study Guide: Exam 010 v1.6, 3rd Edition, chapter 3, page 67.

The /etc/passwd file is a plain text-based database that contains information for all user accounts on the system. It is owned by root and has 644 permissions. The file can only be modified by root or users with sudo privileges and readable by all system users. Each line of the /etc/passwd file contains seven comma-separated fields, representing a user account. The fields are as follows:

• Username: The string you type when you log into the system. Each username must be a unique string on the machine. The maximum length of the username is restricted to 32 characters.
• Password: In older Linux systems, the user’s encrypted password was stored in the /etc/passwd file. On most modern systems, this field is set to x, and the user password is stored in the /etc/shadow file.
• User ID (UID): The user identifier is a number assigned to each user by the operating system to refer to a user. It is used by the kernel to check for the user privileges and grant access to system resources. The UID 0 is reserved for the root user and cannot be assigned to any other user.
• Group ID (GID): The user’s group identifier number, referring to the user’s primary group. When a user creates a file, the file’s group is set to this group. Typically, the name of the group is the same as the name of the user. User’s secondary groups are listed in the /etc/group file.
• User ID Info (GECOS): This is a comment field. This field contains a list of comma-separated values with the following information: User’s full name or the application name, Room number, Work phone number, Home phone number, Other contact information.
• Home directory: The absolute path to the user’s home directory. It contains the user’s files and configurations. By default, the user home directories are named after the name of the user and created under the /home directory.
• Login shell: The absolute path to the user’s login shell. This is the shell that is started when the user logs into the system. On most Linux distributions, the default login shell is Bash.

Therefore, the correct answers are B, C, and E. The user’s storage space limit (A) is not stored in the /etc/passwd file, but in the /etc/quota file. The encrypted password (D) is not stored in the /etc/passwd file, but in the /etc/shadow file. 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.
• Understanding the /etc/passwd File | Linuxize
• Understanding the /etc/passwd File - GeeksforGeeks
• passwd(5) - Linux manual page - man7.org
• Understanding /etc/passwd file in Linux - DEV Community

 Reverse DNS lookups query DNS servers for a PTR (pointer) record; if the server does not have a PTR record, it cannot resolve a reverse lookup. PTR records store IP addresses with their segments reversed, and they append “.in-addr.arpa” to that. For example, if a domain has an IP address of 192.0.2.1, the PTR record will store the domain’s information under 1.2.0.192.in-addr.arpa. In IPv6, the latest version of the Internet Protocol, PTR records are stored within the “.ip6.arpa” domain instead of ".in-addr.arpa."1 Therefore, the name of the IP address 198.51.100.165 is stored in the PTR record for 165.100.51.198.in-addr.arpa. References: 1: Reverse DNS lookup - Wikipedia 1