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

 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 correct crontab entry to execute the script chklog three times per month between 3 p.m. and 5 p.m. is:

3 15,16,17 * * * chklog

The crontab entry has five fields that specify the time and frequency of the job, followed by the command or script to be executed. The fields are:

Minute: the minute of the hour when the job should run, from 0 to 59

Hour: the hour of the day when the job should run, from 0 to 23 (in 24-hour format)

Day of month: the day of the month when the job should run, from 1 to 31

Month: the month of the year when the job should run, from 1 to 12

Day of week: the day of the week when the job should run, from 0 to 6 (where 0 and 7 are Sunday)

The asterisk (*) means any value, and the comma (,) means a list of values. Therefore, the crontab entry above means:

Run the job at the 3rd minute of the hour

Run the job at the 15th, 16th, and 17th hour of the day (which are 3 p.m., 4 p.m., and 5 p.m.)

Run the job on any day of the month

Run the job on any month of the year

Run the job on any day of the week

This will execute the script chklog three times per day, every day of the month, and every month of the year, which is equivalent to three times per month.

The other options are incorrect because:

A. This will run the job at any minute of the hour, but only at the 3rd, 4th, and 5th hour of the day (which are 3 a.m., 4 a.m., and 5 a.m.), and only on the 1st day of the month.

B. This will run the job at the 3rd minute of the hour, but only at the 3rd, 4th, and 5th hour of the day (which are 3 a.m., 4 a.m., and 5 a.m.), and only on the 1st day of the month.

D. This will run the job at the 0th minute of the hour (which is the top of the hour), but only at the 15th, 16th, and 17th hour of the day (which are 3 p.m., 4 p.m., and 5 p.m.), and only on the 1st day of the month.

E. This will run the job at any minute of the hour, but only at the 15th, 16th, and 17th hour of the day (which are 3 p.m., 4 p.m., and 5 p.m.), and only on the 1st day of the month.

References:

Crontab Explained in Linux [With Examples]

‘crontab’ in Linux with Examples - GeeksforGeeks

Linux Crontab Command Help and Examples - Computer Hope

Crontab in Linux with 20 Useful Examples to Schedule Jobs - TecAdmin

Linux crontab tutorial with Examples - Linux Tutorials - Learn Linux …

The crontab file format consists of six fields: minute, hour, day of month, month, day of week, and command. The user-specific crontab files have the same format as the global /etc/crontab file, except that they do not have the username field. The username field is only present in the system-wide crontab files and specifies which user will run the cron job. The year field is not a valid crontab field and is not supported by cron. References:

Scheduling Cron Jobs with Crontab | Linuxize

Crontab Explained in Linux [With Examples]

The chage command can change the following parameters related to user password expiry and aging:

The last password change date (-d or --lastday option)

The password expiry date (-E or --expiredate option)

The minimum number of days between password changes (-m or --mindays option)

The maximum number of days during which a password is valid (-M or --maxdays option)

The number of days of warning before password expires (-W or --warndays option)

The chage command cannot change the number of days of inactivity after a password has expired before the account is locked. This parameter is controlled by the -I or --inactive option of the usermod command, which modifies the user account information. The chage command only displays the current value of this parameter, but does not allow changing it. References:

chage command in Linux with examples - GeeksforGeeks

10 chage command examples in Linux [Cheat Sheet] - GoLinuxCloud

How to Use the Chage Command in Linux – TecAdmin

How to Manage User Password Expiration and Aging in Linux - Tecmint

The /etc/at.deny file specifies the user accounts that can NOT submit jobs via at or batch. The format of the file is a list of usernames, one on each line. Whitespace is not permitted. The superuser may always use at. If the file /etc/at.allow exists, only usernames mentioned in it are allowed to use at. If /etc/at.allow does not exist, /etc/at.deny is checked12. The at and batch commands use the files /usr/lib/cron/at.allow and /usr/lib/cron/at.deny to restrict usage on some systems3. References:

at.allow(5) - Linux man page

at.deny(5) [linux man page] - The UNIX and Linux Forums

The at.allow and at.deny files - IBM

The command that can be used to convert text files in one character encoding to another character encoding is:

iconv: this command can convert text files from one form of encoding to another, such as UTF-8, ISO-8859-1, ASCII, etc. To use this command, you need to specify the input encoding, the output encoding, and the file name. For example, to convert a file named input.txt from ISO-8859-1 to UTF-8, you can run:

iconv -f ISO-8859-1 -t UTF-8 input.txt

The output will be printed to the standard output, which can be redirected to another file or piped to another command. You can also use the -o option to specify the output file name. For example, to convert the same file and save the output to output.txt, you can run:

iconv -f ISO-8859-1 -t UTF-8 -o output.txt input.txt

To list all the supported encodings, you can use the -l option. For example, to see all the encodings that start with UTF, you can run:

iconv -l | grep UTF

The iconv command is part of the GNU libc package and is available on most Linux systems. The full path of the command is /usr/bin/iconv.

The other options are incorrect because:

cat: this command can concatenate and print files to the standard output, but it does not perform any encoding conversion. It can be used to display the contents of a text file, but it will not change the encoding of the file.

convert: this command can convert image files from one format to another, such as PNG, JPEG, GIF, etc. It is part of the ImageMagick suite of tools and is not related to text encoding conversion.

dd: this command can copy and convert data from one source to another, such as files, devices, or pipes. It can perform some conversions, such as changing the case of letters, swapping bytes, or converting between ASCII and EBCDIC, but it does not support common text encodings such as UTF-8 or ISO-8859-1.

utf2utf: this is not a valid command on Linux. There is no such tool that can convert between different UTF encodings.

References:

How to Convert Files to UTF-8 Encoding in Linux - Tecmint

Best way to convert text files between character sets? - Stack Overflow

how to change encoding of a text file without openning the file in shell program - Stack Overflow

HowTo: Check and Change File Encoding In Linux - ShellHacks

How to change character encoding of a text file on Linux - Xmodulo

 The file that specifies the default wallpaper for XDM is /etc/X11/xdm/Xsetup. XDM is a display manager for the X Window System that provides a graphical login screen and manages user sessions. The /etc/X11/xdm/Xsetup file is executed when XDM starts the X server and before any user login or session starts. This file can be used to configure the X server, set X resources, and perform any other system-wide setup tasks, such as setting the wallpaper. To set the wallpaper, one can use a command like qiv -z /usr/local/share/backgrounds/wallpaper.jpg in the /etc/X11/xdm/Xsetup file, where qiv is an image viewer and /usr/local/share/backgrounds/wallpaper.jpg is the path to the desired wallpaper image1.

The other options are not correct/etc/X11/xdm.conf is the configuration file for XDM, which specifies how XDM should behave, such as the access control, the login window, and the session types2/etc/X11/xdm/Defaults is the directory where the default XDM configuration files are stored, such as Xresources, Xsession, and Xwilling2. /etc/X11/defaults.conf is not a valid file or directory related to XDM or X Window System. References:

XDM - ArchWiki

Configuring XDM - Linux Documentation Project

 The correct format for the DISPLAY environment variable is hostname:displaynumber.screennumber, where hostname is the name of the computer where the X server runs, displaynumber is a sequence number (usually 0) that identifies a display, and screennumber is the number of the screen within that display (usually 0). The screennumber can be omitted if it is 0. For example, localhost:0 or myhost:1.0 are valid values for the DISPLAY variable. The other options are either missing the colon, using the wrong separator, or not specifying the display number. References:

X11 - DISPLAY (environment variable) - Datacadamia

x11 - How can I specify a display? - Stack Overflow

What is the $DISPLAY environment variable? - Ask Ubuntu