LPI Updated 010-160 Exam Questions and Answers by patricia

 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

The su command stands for substitute user or switch user. It allows you to run a shell or a command as another user, usually the superuser or root. To use the su command, you need to know the password of the target user. For example, if you want to switch to the root user, you can type su - and enter the root password. This will give you a root shell, where you can execute commands with administrative privileges. To exit the root shell, you can type exit or press Ctrl-D. The su command is not the default shell of the root account, nor can it only be used by the root user. It can be used by any user who knows the password of another user. The su command does not change the name of the main administrator account, which is always root on Linux systems. The su command also does not lock the root account in specific time frames, although there are other ways to do that, such as using the pam_time module. References:

• Linux Essentials - Linux Professional Institute (LPI), section 5.1.1
• LPI Linux Essentials Study Guide: Exam 010 v1.6, 3rd Edition, chapter 9, page 219.

The correct command to change the ownership of the file doku.odt to a new owner named tux is chown tux doku.odt. This command uses the chown command, which stands for change owner, followed by the name of the new owner and the name of the file as arguments. The chown command allows you to change the user and/or group ownership of a given file, directory, or symbolic link12. The other options are incorrect because they use different commands or syntax that do not change the ownership of the file. For example:

• Option A uses the chmod command, which stands for change mode, and is used to change the permissions of files and directories, not the ownership3.
• Option B uses the newuser command, which is used to create a new user account, not to change the ownership of a file4.
• Option D uses the transfer command, which is not a valid Linux command.
• Option E uses the passwd command, which is used to change the password of a user account, not the ownership of a file5.

References: 1: Chown Command in Linux (File Ownership) | Linuxize 2: chown command in Linux with Examples - GeeksforGeeks 3: Chmod Command in Linux (File Permissions) | Linuxize 4: newusers(8) - Linux man page 5: passwd(1) - Linux man page

The commands man ls and info ls are used to get information on the proper use of ls. The man command displays the manual page for a given command, which contains a description, synopsis, options, examples, and other details. The info command displays the info page for a given command, which is similar to the manual page but may have more information and hyperlinks. The option ls, usage ls, and manual ls commands are not valid commands in Linux and will result in an error message. References:

• Linux Essentials Exam Objectives, Version 1.6, Topic 103.1, Weight 2
• Linux Essentials Certification Guide, Chapter 3, Page 51-52
• Ls Command in Linux (List Files and Directories) | Linuxize