Free Practice Questions for LPI 102-500 Exam

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 /usr/share/zoneinfo directory contains the binary time zone files that are used by the system to determine the local time for any region. The files are organized in subdirectories by continent, country, or ocean. Some files represent the standard time zones, while others may have historical or political variations. To set the system’s timezone, one can create a symbolic link from /etc/localtime to the appropriate file in the /usr/share/zoneinfo directory. For example, to set the timezone to America/New_York, one can use the command sudo ln -sf /usr/share/zoneinfo/America/New_York /etc/localtime. Alternatively, one can use the timedatectl command to set the timezone without creating the link manually. References:

How to Set or Change the Time Zone in Linux | Linuxize

4 Ways to Change the Timezone in Linux - wikiHow

The commands that can be used to change a user’s account aging information are:

usermod: this command can modify various user account properties, including the password expiration date, the account expiration date, the minimum and maximum password age, the password warning period, and the password inactivity period. To use this command, you need to specify the option and the value for the property you want to change, followed by the username. For example, to set the password expiration date for the user test to February 11, 2022, you can run:

usermod -e 2022-02-11 test

To view the current account aging information for a user, you can use the -l option with the usermod command. For example, to view the information for the user test, you can run:

usermod -l test

passwd: this command can change the password of a user account, as well as some password aging options. To use this command, you need to specify the username and the option for the property you want to change. For example, to change the password of the user test, you can run:

passwd test

To set the maximum password age for the user test to 90 days, you can run:

passwd -x 90 test

To view the current password aging information for a user, you can use the -S option with the passwd command. For example, to view the information for the user test, you can run:

passwd -S test

chage: this command can change the user password expiry and aging information, such as the password expiration date, the account expiration date, the minimum and maximum password age, the password warning period, and the password inactivity period. To use this command, you need to specify the option and the value for the property you want to change, followed by the username. For example, to set the account expiration date for the user test to February 11, 2022, you can run:

chage -E 2022-02-11 test

To view the current account aging information for a user, you can use the -l option with the chage command. For example, to view the information for the user test, you can run:

chage -l test

The other options are incorrect because:

chattr: this command can change the file attributes on a Linux file system, such as making a file immutable, append-only, or undeletable. It has nothing to do with user account aging information.

chsh: this command can change the login shell of a user account, such as bash, zsh, or ksh. It has nothing to do with user account aging information.

References:

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

Use the Chage Command in Linux

How to set user password expirations on Linux | Enable Sysadmin

How to change password and account expiry options on Linux using chage - Linux Tutorials - Learn Linux Configuration

3 ways to change user password expiration date in Linux - howtouselinux

The /etc/passwd file stores local accounts of the system. It is a readable text file and uses colons (:) to separate the fields. This file helps with converting user IDs to names (and back). It is fine that all users can read this file, but they should not be able to change fields. Therefore, the most correct permissions for /etc/passwd are -rw-r–r–, which means that only the owner (root) can write to the file, and everyone can read it. The /etc/shadow file contains information about the system’s users’ passwords. It is owned by user root and group shadow, and has 640 permissions. The password is stored as a long string of characters, which is a combination of the hashing algorithm, optional salt applied, and the hashed password itself. Other users are not allowed to read the file directly, to prevent them from gathering hashed passwords of others. Therefore, the most correct permissions for /etc/shadow are -r--------, which means that only the owner (root) can read the file, and no one else can read or write to it. References:

The user-specific crontab files are stored in the /var/spool/cron/crontabs directory, where each file is named after the username of the owner. These files are not meant to be edited directly, but rather through the crontab command. The other options are either incorrect or non-existent locations for user crontab files. References:

Where is the user crontab stored?

crontab running as a specific user

Location of the crontab file

Where is the User Crontab Stored?

The /etc/group file is a text file that defines the groups and their members on the system. Each line in the file represents a single group, with the following format:

group_name:password:GID:user_list

The fields are:

group_name: the name of the group

password: the (encrypted) group password, or empty for no password

GID: the numerical group ID

user_list: a comma-separated list of users who belong to the group

Therefore, the fields that can be found in the /etc/group file are the name of the group, the password of the group, and the list of users that belong to the group. The home directory and the description of the group are not part of the /etc/group file format. References:

group(5) - Linux manual page

/etc/group file format | Linux#

The command userdel --force --remove bob is used to delete the user account named bob and all its associated files. The --force option forces the removal of the user account, even if the user is still logged in. The --remove option forces userdel to remove the user’s home directory and mail spool, even if another user uses the same home directory or if the mail spool is not owned by the specified user12. Therefore, options A and B are true regarding this command.

The other options are not true because:

Option C is false because the locate database is not updated by the userdel command. The locate database is updated by the updatedb command, which is usually run by cron as a scheduled job3.

Option D is false because the userdel command does not remove all files owned by bob from all mounted filesystems. The userdel command only removes the user’s home directory and mail spool, and it does not search for and delete the user files located in other file systems. You have to search for and delete the files manually1.

Option E is false because the userdel command does not delete the group with the same name as the user, unless the USERGROUPS_ENAB parameter is set to yes in the /etc/login.defs file and the group has no other members14.

References:

How to Delete/Remove Users in Linux (userdel Command) | Linuxize

userdel(8) — Linux manual page

updatedb(8) — Linux manual page

Understanding the /etc/login.defs File | Linuxize

The usermod command is a utility for modifying user accounts. One of its options is -G, which allows specifying a list of supplementary groups that the user is a member of. If the user is currently a member of a group that is not listed, the user will be removed from that group. For example, to remove the user alice from the group sales, one can use the command sudo usermod -G admin alice, assuming that alice is only a member of admin and sales groups. Alternatively, one can use the gpasswd command with the --delete option to remove a user from a specific group without affecting other groups. For example, to remove the user alice from the group sales, one can use the command sudo gpasswd --delete alice sales. The other commands in the options are not used for removing a user from a group. The grouprm command does not exist. The groupmod command is used for modifying group attributes, not membership. The passwd command is used for changing user passwords, not groups. The usergroups command is used for displaying the groups that a user belongs to, not modifying them. References:

usermod(8) - Linux man page

gpasswd(1) - Linux man page

How to Remove User From Group in Linux [Quick Tip]

A default route is a special type of route that specifies where to send packets when there is no explicit route for the destination in the routing table. A default route is usually configured on a router or a gateway that connects to another network, such as the internet. A default route is often represented by the destination 0.0.0.0/0, which means any IP address.

A default route is not always used first. It is only used as a last resort, when there is no more specific route for the destination. For example, if a host wants to send a packet to 192.168.1.10, and the routing table contains the following entries:

Destination Gateway Genmask Flags Metric Ref Use Iface 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 eth0

The host will use the first entry, which is more specific, and send the packet directly to 192.168.1.10 via eth0 interface. The second entry, which is the default route, will not be used in this case. However, if the host wants to send a packet to 8.8.8.8, which is not in the same network, the host will use the default route and send the packet to 192.168.1.1, which is the gateway to the internet.

Setting a default route does not disable other routes. It only adds an entry to the routing table that can be used when no other route matches the destination. Other routes are still valid and can be used if they are more specific.

Without a default route, network communication in directly attached networks is still possible, as long as there are routes for those networks in the routing table. However, network communication to other networks that are not directly connected will not be possible, unless there are specific routes for those networks in the routing table.

References:

How to Set the Default Gateway in Linux - How-To Geek

Linux setup default gateway with route command - nixCraft

How to set a default route permanently in Linux - Xmodulo

 The hostname command is used to set the hostname of the local system. The hostname command can take a single argument, which is the new hostname to be assigned to the system. For example, to set the hostname to linux, one can run:

hostname linux

The hostname command can also be used without any arguments to display the current hostname of the system. For example, to show the current hostname, one can run:

hostname

The hostname command only changes the hostname temporarily, meaning that the original hostname will be restored after a reboot. To change the hostname permanently, one has to edit the configuration files that store the hostname information, such as /etc/hostname, /etc/hosts, /etc/sysconfig/network, etc. The exact files and commands may vary depending on the Linux distribution and the system initialization process. For more details, please refer to the web search results1 or the question answering results2. References: