LPI 102-500 - LPIC-1 Exam 102, Part 2 of 2, version 5.0

The sudo configuration file (/etc/sudoers) defines the rules for granting privileges to users or groups to execute commands as another user, usually the superuser or root. The format of the sudo configuration file is as follows:

user_list host_list=effective_user_list tag_list command_list

The user_list specifies the users who can run the commands, the host_list specifies the hosts where the commands can be run, the effective_user_list specifies the user as whom the commands can be run, the tag_list specifies some options for the commands, and the command_list specifies the commands that can be run.

In this case, the user_list is jane, the host_list is ANY (meaning any host), the effective_user_list is not specified (meaning root by default), the tag_list is NOPASSWD or PASSWD (meaning whether a password is required or not), and the command_list is /bin/kill, /bin/id, or /sbin/fdisk.

Therefore, the sudo configuration file allows jane to run /bin/kill, /bin/id, or /sbin/fdisk as root on any host, but with different password requirements. Specifically:

Jane can run /bin/kill without specifying a password, because the tag_list is NOPASSWD for this command. This means that jane can execute sudo /bin/kill and the command will run as root without asking for any password. This makes option D true.

Jane can run /bin/id without specifying a password, because the tag_list is also NOPASSWD for this command. This means that jane can execute sudo /bin/id and the command will run as root without asking for any password. This makes option E true.

Jane can run /sbin/fdisk after specifying her password, because the tag_list is PASSWD for this command. This means that jane can execute sudo /sbin/fdisk and the command will ask for jane’s password before running as root. This makes option C true.

The other options are false because:

Jane cannot run /bin/id only after specifying her password, because the tag_list is NOPASSWD for this command. This makes option A false.

Jane cannot run /sbin/fdisk after specifying root’s password, because the password that is required is jane’s password, not root’s password. This makes option B false.

References:

LPI Linux Essentials: 1.4. Using sudo

LPI Linux Administrator: 102.5. Use Debian package management

LPI Linux Engineer: 201.1. Measure and Troubleshoot Resource Usage

LPI Linux Professional Certification Program

On a machine running several X servers, programs identify the different instances of the X11 server by a display name like :1. The display name consists of three parts: the hostname, the display number, and the screen number. The hostname is the name of the machine where the X server runs. The display number is a unique identifier that distinguishes different X server instances on the same machine. The screen number is used to address different physical screens that are managed by the same X server instance. The display name has the format hostname:displaynumber.screennumber. If the hostname is omitted, it means the local machine. The screen number is also optional and defaults to 0. For example, :1 means the second X server instance on the local machine, screen 0. remote:0.1 means the first X server instance on the remote machine, screen 1. The display name is part of the topic 106.1: Install and configure X11, which is one of the objectives of the LPI Linux Administrator - 102 exam12. References: 1: LPI Linux Administrator - 102 (LPIC-1) 2: Exam 102 Objectives

The lpq command, meaning list print queue, is a command-line utility in the Linux system to display the status of the print queue for a specified printer or class1. The lpq command can take various options and arguments to filter and format the output. By default, the lpq command shows the print queue for the default printer or class, which is determined by the PRINTER or LPDEST environment variables, or the /etc/printcap file. For example, to display the print queue for the default printer, one can run:

lpq

The output shows the printer name, status, rank, owner, job number, file size, and file name for each print job. For example, the output may look like:

Printer: lp@localhost ‘HP LaserJet 1020’ Queue: no printable jobs in queue Server: no server active Status: printer idle. enabled since Tue 09 Nov 2021 10:00:00 AM EST Rank Owner Job File(s) Total Size 1st alice 123 report.pdf 1024 bytes 2nd bob 124 memo.docx 2048 bytes 3rd charlie 125 presentation.pptx 4096 bytes

This shows that there are three print jobs in the queue for the printer lp@localhost, which is an HP LaserJet 1020. The first job belongs to alice, the second to bob, and the third to charlie. The lpq command can also display the print queue for a specific printer or class by using the -P option, followed by the printer or class name. For example, to display the print queue for the printer lp1, one can run:

lpq -P lp1

The output shows the print queue for the printer lp1, which may be different from the default printer. The lpq command can also display the print queue for all printers or classes by using the -a option. For example, to display the print queue for all printers or classes, one can run:

lpq -a

The output shows the print queue for each printer or class, separated by a blank line. The lpq command is different from the following commands:

lpd: This is not a command, but a daemon that provides print spooling and network printing services for the Linux system2. The lpd daemon is started by the system initialization scripts and runs in the background. It does not display the print queue for any printer or class.

lpr: This is a command that submits print jobs to the print queue for a specified printer or class3. The lpr command can take various options and arguments to specify the print options and the files to be printed. For example, to print the file report.pdf to the default printer, one can run:

lpr report.pdf

The lpr command does not display the print queue for any printer or class.

lp: This is a command that submits print jobs to the print queue for a specified printer or class, similar to the lpr command4. The lp command can take various options and arguments to specify the print options and the files to be printed. For example, to print the file report.pdf to the printer lp1, one can run:

lp -d lp1 report.pdf

The lp command does not display the print queue for any printer or class.

lsq: This is not a valid command in the Linux system. It may be a typo or a misspelling of the lpq command. It does not display the print queue for any printer or class. References:

1

The command journalctl is included in systemd and supports selecting messages from the systemd journal by criteria such as time or unit name. The systemd journal is a binary log file that stores system and service messages. The journalctl command can be used to view, filter, export, and manipulate the journal entries. For example, to show all messages from a specific unit, such as sshd.service, the command would be:

journalctl -u sshd.service

To show all messages from a specific time range, such as yesterday, the command would be:

journalctl --since=yesterday

The journalctl command has many options and arguments that can be used to customize the output and perform various operations on the journal. For more information, see the man page of journalctl or the official documentation1. References: [LPI 102-500 Exam Objectives], Topic 106.2: System logging, Weight: 3. [systemd-journald.service(8) — systemd — Debian unstable — Debian Manpages], Section NAME.

The configuration file that contains the default options for SSH clients is /etc/ssh/ssh_config. This file is read by the ssh program when it connects to a remote SSH server. It can contain global options that apply to all hosts, or host-specific options that only apply to certain hosts or patterns. The /etc/ssh/ssh_config file is the system-wide default SSH client configuration file. It can be overridden by a user-specific configuration file ~/.ssh/config, which is located in the user’s home directory. The /etc/ssh/ssh_config file is part of the topic 110.1: Perform security administration tasks, which is one of the objectives of the LPI Linux Administrator - 102 exam12. References: 1: LPI Linux Administrator - 102 (LPIC-1) 2: Exam 102 Objectives

Broadcast addresses are used to send a message to all devices on a network segment. IPv4 supports broadcast addresses, but IPv6 does not. Instead, IPv6 uses multicast addresses, which are used to send a message to a group of devices that have joined a multicast group. Multicast addresses are more efficient and flexible than broadcast addresses, as they allow the sender to specify the recipients more precisely and avoid unnecessary network traffic. IPv6 also supports anycast addresses, which are used to send a message to the nearest device that provides a specific service. Anycast addresses are useful for load balancing and redundancy. References:

[LPI Linux Administrator - Exam 102 Objectives - Topic 109: Networking Fundamentals]

IPv6 - Features - Online Tutorials Library

IPv6 - Wikipedia

The traceroute program can be used to determine the routing path to a given destination by sending packets with incrementing TTL values and recording the source of the ICMP time exceeded messages. This way, it can show the intermediate hops and the round-trip times for each packet. The other programs have different purposes: dig is used to query DNS servers, netstat is used to display network connections and statistics, ping is used to test the reachability of a host by sending ICMP echo requests and measuring the response time, and route is used to manipulate the routing table. References:

LPI 102-500 Exam Objectives, Topic 110: Network Fundamentals, Weight: 4, 110.3 Basic network troubleshooting

LPI 102-500 Study Guide, Chapter 10: Network Fundamentals, Section 10.3: Basic Network Troubleshooting, Page 125-126

The route command displays the kernel’s routing table, which contains information about how packets are routed to different destinations. By default, route tries to resolve the IP addresses of the routers and destinations to their hostnames using DNS. If DNS is not working properly, this can cause a delay in displaying the routing table as route waits for the DNS queries to time out. To avoid this, route can be used with the -n option, which prevents DNS lookups and displays only numeric addresses. References:

LPI 102-500 Exam Objectives, Topic 109: Network Fundamentals, 109.3 Basic network troubleshooting

LPI 102-500 Study Guide, Chapter 9: Network Troubleshooting, Section 9.2: Troubleshooting Routing Problems

 The nsswitch.conf file is a configuration file that determines the sources and the order of the sources that are queried for various system databases, such as user information, group information, host names, network services, and more. The C library uses this file to look up various system information when a program or a command requests it. For example, when a user logs in, the C library will use the nsswitch.conf file to determine where to find the user’s password, whether it is in the local /etc/passwd file, or in a remote LDAP server, or both. The nsswitch.conf file allows the system administrator to configure the system databases in a flexible and modular way. References:

[LPI Linux Essentials - Topic 106: The Linux Operating System]

[LPI Linux Administrator - Exam 102 Objectives - Topic 110: Security]

[Linux man page for nsswitch.conf]