LPI Updated 102-500 Exam Questions and Answers by ayden

The command that must be run in order to ensure the MTA knows about the new email alias is:

newaliases

This command updates the MTA’s aliases database and makes the changes effective. It is equivalent to the commands sendmail -bi or sendmail -I12. The newaliases command should be run after making modifications to the /etc/aliases file, which contains the email aliases for the system3.

 The batch command is similar to the at command, except that it executes commands when the system load levels permit; in other words, when the load average drops below 1.5, or the value specified in the invocation of atd1. The at command allows us to schedule jobs using any of two commands: at and batch. While at runs commands at our specified time, batch runs commands when our system’s load average is below 0.82. Both commands read commands from standard input or a specified file, and both commands send the output of the commands to the user by mail1. Therefore, the main difference between them is the time of execution: at runs at a fixed time, while batch runs when the system is idle. References: 1: Linux At, Batch, Atq, Atrm Command Help and Examples - Computer Hope 2: The “at” Command in Linux | Baeldung on Linux

 The commands that should be added to /etc/bash_profile to change the language of messages from an internationalised program to Portuguese (pt) are:

export LANG=“pt”

export LC_MESSAGES=“pt”

 The LANG and LC_MESSAGES environment variables are used to control the language of messages from an internationalised program. The LANG variable sets the default locale for all categories, such as collation, currency, date and time formats, etc. The LC_MESSAGES variable sets the locale for the language of messages, overriding the LANG variable for this category. Therefore, to change the language of messages to Portuguese, both variables should be set to “pt” in /etc/bash_profile, which is a script that is executed when a user logs in. This will affect the current user and any subsequent login sessions.

References:

Locale Environment Variables in Linux – Baeldung on Linux

Environment Variables - The Open Group

[LPI Linux Essentials - 1.4 Localization and Internationalization]

 The crontab entry that could be used to set the system time at regular intervals is the one that uses the ntpdate command to synchronize the system clock with a Network Time Protocol (NTP) server. The ntpdate command takes one or more NTP server names or IP addresses as arguments and adjusts the system clock accordingly12. The crontab entry B specifies that the ntpdate command should be executed at the first minute of the zeroth hour (i.e., 00:01) of every day of every month of every weekday, using the NTP server ntp1.digex.net34. This will ensure that the system time is updated daily with a reliable source.

The other crontab entries are either invalid or ineffective for setting the system time at regular intervals. The date command can be used to display or set the system date and time, but it requires a specific format for the argument, not an NTP server name5. The runcron and settime commands are not standard Linux commands and their functionality is unknown. The $d, $t, and $24 variables are also undefined and meaningless in this context.

References: 1: Linux At, Batch, Atq, Atrm Command Help and Examples - Computer Hope 2: How to set a cron job to run at a exact time? - Stack Overflow 3: 107.2 Lesson 1 - Linux Professional Institute Certification Programs 4: How to setup a crontab to execute at specific time - Stack Overflow 5: Writing a specific format of time in a text file every minute using … - Ask Ubuntu