LPI Updated 102-500 Exam Questions and Answers by ismail

In bash, the PID of a shell script’s subshell process is stored in a special variable called $$. This variable is read-only, and you cannot modify it in a shell script1. You can use echo $$ to get the PID of the current bash shell you are using2. Therefore, when the command echo $$ outputs 12942, it means that the PID of the current shell is 12942. References:

[LPI Linux Essentials - Topic 103: Command Line Basics]

[Bash Special Parameters]

How to get the process ID (PID) of a shell script

How to know the process id of current bash session?

The syslog.conf file is the main configuration file for the syslogd daemon, which logs system messages on Linux systems. This file specifies rules for logging, using a selector field and an action field. The selector field consists of a facility and a priority, separated by a period. The facility indicates the subsystem that produced the message, such as mail, auth, or kern. The priority indicates the severity of the message, such as debug, info, or emerg. An asterisk (*) stands for all facilities or all priorities, depending on where it is used. The action field specifies where the message should be logged, such as a file, a user, or a device.

To have all syslog messages generated by the system go to virtual console 12, which is represented by the device file /dev/tty12, the following entry can be added to the syslog.conf file:

 /dev/tty12

This means that any facility and any priority (.) should be logged to the device /dev/tty12. This will redirect all the messages that would normally go to /var/log/messages to the console 12. To see the messages, the user can press Ctrl-Alt-F12 to switch to that console.

References:

syslog.conf (5) - Linux man page

Beginner’s Guide to Syslogs in Linux [Real World Examples]

Configuration Formats — rsyslog 8.33-20180109-54df0f2 documentation

The ntpdate command is a tool used to synchronize the system date and time with the NTP (Network Time Protocol) server(s) specified as arguments. It can be run manually as necessary to set the system clock, or it can be run from a cron script to periodically update the system clock. The ntpdate command has the following syntax:

ntpdate [options] server [server ...]

The ntpdate command obtains a number of samples from each server and applies a subset of the NTP clock filter and selection algorithms to select the best one. It then adjusts the system clock either by stepping it (if the offset is larger than 0.5 seconds) or by slewing it (if the offset is smaller than 0.5 seconds). The ntpdate command can also be used to query the date and time from a server without setting the system clock by using the -q option.

The other statements are false because:

It is not the primary management command for the NTP time server. The primary management command for the NTP time server is ntpd, which is a daemon that runs continuously and disciplines the system clock using sophisticated algorithms.

It updates both the local system’s date and time, not just the date. The ntpdate command sets the system date and time according to the configured timezone information.

It does not send the local system time to any remote NTP time servers. The ntpdate command only queries the time from the servers and does not transmit any time information to them.

It cannot be used by any user to set the user clock independently of the system clock. The ntpdate command must be run as root on the local host and it affects the system clock for all users.

References:

Linux ntpdate Command Tutorial – LinuxTect

ntpdate - set the date and time via NTP

How to Use NTPDATE to Sync Time in Ubuntu Linux? – TheITBros

The command lpq can be used to display the status of the printer’s queue on a Linux server. The lpq command is part of the cups-bsd package, which provides the Berkeley commands for CUPS (Common UNIX Printing System), the standard printing system for Linux. The lpq command shows the status of a specified printer or the default printer if none is specified. It also lists the jobs that are queued for printing, along with their job IDs, owners, sizes, and names12. For example, to display the status of the printer lp1, we can use the following command:

$ lpq -P lp1

lp1 is ready

Rank Owner Job File(s) Total Size

active user1 123 test.txt 1024 bytes

1st user2 124 report.pdf 2048 bytes

The output shows that the printer lp1 is ready, and that there are two jobs in the queue, one of which is active and the other is waiting. The output also shows the owners, job IDs, file names, and sizes of the jobs. To display the status of all printers, we can use the -a option:

$ lpq -a

lp1 is ready

Rank Owner Job File(s) Total Size

active user1 123 test.txt 1024 bytes

1st user2 124 report.pdf 2048 bytes

lp2 is ready

no entries

The output shows that there are two printers, lp1 and lp2, and that lp2 has no entries in the queue. To display more information about the jobs, such as the priority, submission time, and status, we can use the -l option:

$ lpq -l -P lp1

lp1 is ready

Rank Owner Job File(s) Total Size

active user1 123 test.txt 1024 bytes

priority 50 Apr 27 10:00 processing since Apr 27 10:01

1st user2 124 report.pdf 2048 bytes

priority 50 Apr 27 10:05 waiting for lp1

The output shows that the jobs have the same priority, and that the first job is processing while the second job is waiting. The lpq command can be useful for troubleshooting printing problems, such as checking if the printer is ready, if there are any stuck or failed jobs, or if there are any conflicts or delays in the queue34. References: 1: lpq(1) - Linux manual page 2: How to Use the lp Command in Linux to Print Files From Terminal - Make Tech Easier 3: Linux sysadmin printing reference guide - PenguinTutor 4: How to manage print jobs on Linux - Network World