Practice Free 102-500 Exam Online Questions
Question #21
Of the ways listed, which is the best method to temporarily suspend a user’s ability to interactively login?
- A . Use passwd -d username to give the user an empty password.
- B . Use chage to expire the user account.
- C . Change the user’s password.
- D . Add the command exit to the user’s .login file.
Correct Answer: B
B
Explanation:
The chage command can be used to change the expiration date of a user account. By setting the
expiration date to a past date, the user account will be disabled and the user will not be able to login
interactively. This is a temporary method, as the expiration date can be changed back to a future
date or removed to re-enable the user account. The other options are either permanent, insecure, or
ineffective. Option A is insecure, as it allows anyone to login as the user without a password. Option
C is permanent, as it changes the user’s password without saving the original one. Option D is
ineffective, as it only affects the user’s .login file, which is used by the csh and tcsh shells, and not by
other shells such as bash or zsh. Therefore, option B is the best method to temporarily suspend a
user’s ability to interactively login.
Reference:
https://linuxconfig.org/disabling-user-logins-to-linux-system
https://askubuntu.com/questions/282806/how-to-enable-or-disable-a-user
B
Explanation:
The chage command can be used to change the expiration date of a user account. By setting the
expiration date to a past date, the user account will be disabled and the user will not be able to login
interactively. This is a temporary method, as the expiration date can be changed back to a future
date or removed to re-enable the user account. The other options are either permanent, insecure, or
ineffective. Option A is insecure, as it allows anyone to login as the user without a password. Option
C is permanent, as it changes the user’s password without saving the original one. Option D is
ineffective, as it only affects the user’s .login file, which is used by the csh and tcsh shells, and not by
other shells such as bash or zsh. Therefore, option B is the best method to temporarily suspend a
user’s ability to interactively login.
Reference:
https://linuxconfig.org/disabling-user-logins-to-linux-system
https://askubuntu.com/questions/282806/how-to-enable-or-disable-a-user
Question #22
What command displays all aliases defined in the current shell? (Specify the command without any path information)
Correct Answer: alias, alias -p
Explanation:
The alias command is used to create, list, or remove aliases in the current shell. An alias is a short name that refers to another command, usually with some options or arguments. Aliases are useful for saving typing time, avoiding spelling errors, or customizing the behavior of commands. To list all the aliases defined in the current shell, we can use the alias command without any arguments. This will print the aliases in the format of alias name=’command’123. For example:
$ alias alias cp=‘cp -i’ alias l=‘ls -CF’ alias la=‘ls -A’ alias ll=‘ls -alF’ alias mv=‘mv -i’ alias rm=‘rm -i’ The output shows that some common commands, such as cp, mv, and rm, have aliases that add the – i option, which prompts the user before overwriting or deleting files. The l, la, and ll aliases are shortcuts for different variations of the ls command, which lists files and directories123.
Reference: 1: List All Available Commands and Aliases in Linux – Baeldung 2: get all aliases in linux
shell – Stack Overflow 3: How to list all aliases on Linux – Linux Tutorials – Learn Linux Configuration
Explanation:
The alias command is used to create, list, or remove aliases in the current shell. An alias is a short name that refers to another command, usually with some options or arguments. Aliases are useful for saving typing time, avoiding spelling errors, or customizing the behavior of commands. To list all the aliases defined in the current shell, we can use the alias command without any arguments. This will print the aliases in the format of alias name=’command’123. For example:
$ alias alias cp=‘cp -i’ alias l=‘ls -CF’ alias la=‘ls -A’ alias ll=‘ls -alF’ alias mv=‘mv -i’ alias rm=‘rm -i’ The output shows that some common commands, such as cp, mv, and rm, have aliases that add the – i option, which prompts the user before overwriting or deleting files. The l, la, and ll aliases are shortcuts for different variations of the ls command, which lists files and directories123.
Reference: 1: List All Available Commands and Aliases in Linux – Baeldung 2: get all aliases in linux
shell – Stack Overflow 3: How to list all aliases on Linux – Linux Tutorials – Learn Linux Configuration
Question #23
Which configuration file would be edited to change default options for the OpenSSH server?
- A . /etc/ssh/sshd_config
- B . /etc/ssh/ssh
- C . /etc/ssh/server
- D . /etc/ssh/ssh_config
- E . /etc/ssh/ssh_server
Correct Answer: A
A
Explanation:
The configuration file for the OpenSSH server is called sshd_config. It is typically located in /etc/ssh on most *NIX systems, but is /etc/sshd_config in the case of MacOS X and perhaps other systems. OpenSSH has two different sets of configuration files: one for client programs (ssh, scp, and sftp) and one for the server daemon (sshd). System-wide SSH configuration information is stored in the /etc/ssh/ directory1.
Reference: 1: Where is the configuration file for OpenSSH server?
A
Explanation:
The configuration file for the OpenSSH server is called sshd_config. It is typically located in /etc/ssh on most *NIX systems, but is /etc/sshd_config in the case of MacOS X and perhaps other systems. OpenSSH has two different sets of configuration files: one for client programs (ssh, scp, and sftp) and one for the server daemon (sshd). System-wide SSH configuration information is stored in the /etc/ssh/ directory1.
Reference: 1: Where is the configuration file for OpenSSH server?
Question #24
Which command, available with all MTAs, is used to list the contents of the MTA’s mail queue? (Specify ONLY the command without any path or parameters.)
Correct Answer: mailq,
/usr/bin/mailq,
sendmail -bp,
/usr/sbin/sendmail –
bp, /usr/lib/sendmail
-bp,
Explanation:
sendmail, /usr/sbin/sendmail, /usr/lib/sendmail
The command that is used to list the contents of the MTA’s mail queue is mailq12. This command is available with all MTAs, such as sendmail, postfix, exim, etc12. The mailq command prints the mail queue, which is the list of messages that are waiting to be sent12. The output of the mailq command shows the queue ID, size, time, sender, and recipient of each message12. The mailq command can also take various options to modify the output, such as -v for verbose mode, -Ac for mail submission queue, -qL for lost items, and -qQ for quarantined items3.
Reference: 1: mailq Command in Linux with Examples – GeeksforGeeks 2: mailq Command Examples
in Linux C The Geek Diary 3: linux – How to see entire sendmail queue? – Server Fault
/usr/bin/mailq,
sendmail -bp,
/usr/sbin/sendmail –
bp, /usr/lib/sendmail
-bp,
Explanation:
sendmail, /usr/sbin/sendmail, /usr/lib/sendmail
The command that is used to list the contents of the MTA’s mail queue is mailq12. This command is available with all MTAs, such as sendmail, postfix, exim, etc12. The mailq command prints the mail queue, which is the list of messages that are waiting to be sent12. The output of the mailq command shows the queue ID, size, time, sender, and recipient of each message12. The mailq command can also take various options to modify the output, such as -v for verbose mode, -Ac for mail submission queue, -qL for lost items, and -qQ for quarantined items3.
Reference: 1: mailq Command in Linux with Examples – GeeksforGeeks 2: mailq Command Examples
in Linux C The Geek Diary 3: linux – How to see entire sendmail queue? – Server Fault
Question #25
What is true regarding the command sendmail?
- A . With any MTA, the sendmail command must be run periodically by the cron daemon.
- B . All MTAs, including Postfix and Exim, provide a sendmail command.
- C . The sendmail command prints the MTAs queue history of which mails have been sent successfully.
- D . It is only available when the sendmail MTA is installed.
Correct Answer: B
B
Explanation:
The sendmail command is a generic interface to various mail transfer agents (MTAs), such as Sendmail, Postfix, Exim, Qmail, etc. The sendmail command is used to send emails from the command line or from other programs that need to deliver emails. The sendmail command accepts various flags and parameters to specify the sender, recipient, subject, body, and attachments of the email. The sendmail command also reads the standard input for the email content if no file is specified. The sendmail command is part of the sendmail package, which is the original and most widely used MTA for Unix-like systems. However, other MTAs, such as Postfix and Exim, also provide a sendmail command for compatibility reasons. The sendmail command provided by these MTAs may have slightly different syntax and options, but they all support the basic functionality of sending emails. Therefore, the statement that all MTAs, including Postfix and Exim, provide a sendmail command is true123.
The other statements are false. The sendmail command does not need to be run periodically by the cron daemon, as it is not a daemon itself, but a command-line tool. The sendmail command does not print the MTA’s queue history, but rather sends the email to the MTA for delivery. The sendmail command is not only available when the sendmail MTA is installed, but also when other MTAs that provide a sendmail command are installed.
Reference: 1: Linux Sendmail Command Help and Examples – Computer Hope 2: Send Email in Linux from Command Line | DigitalOcean 3: 5 Ways To Send Email from Linux Command Line – TecAdmin
B
Explanation:
The sendmail command is a generic interface to various mail transfer agents (MTAs), such as Sendmail, Postfix, Exim, Qmail, etc. The sendmail command is used to send emails from the command line or from other programs that need to deliver emails. The sendmail command accepts various flags and parameters to specify the sender, recipient, subject, body, and attachments of the email. The sendmail command also reads the standard input for the email content if no file is specified. The sendmail command is part of the sendmail package, which is the original and most widely used MTA for Unix-like systems. However, other MTAs, such as Postfix and Exim, also provide a sendmail command for compatibility reasons. The sendmail command provided by these MTAs may have slightly different syntax and options, but they all support the basic functionality of sending emails. Therefore, the statement that all MTAs, including Postfix and Exim, provide a sendmail command is true123.
The other statements are false. The sendmail command does not need to be run periodically by the cron daemon, as it is not a daemon itself, but a command-line tool. The sendmail command does not print the MTA’s queue history, but rather sends the email to the MTA for delivery. The sendmail command is not only available when the sendmail MTA is installed, but also when other MTAs that provide a sendmail command are installed.
Reference: 1: Linux Sendmail Command Help and Examples – Computer Hope 2: Send Email in Linux from Command Line | DigitalOcean 3: 5 Ways To Send Email from Linux Command Line – TecAdmin
Question #26
Which of the following options in the chrony configuration file define remote lime sources? (Choose TWO correct answers.)
- A . Source
- B . Clock
- C . Remote
- D . Pool
- E . server
Correct Answer: D, E
Question #27
Which file, if present, must contain all users that are allowed to use the cron scheduling system? (Specify the full name of the file, including path.)
Correct Answer: crontab
Explanation:
The file /etc/cron.allow, if present, must contain all users that are allowed to use the cron scheduling system. This file is used to restrict the access to cron for security reasons. Only users listed in this file can create and edit their own crontab files using the crontab command. If the file does not exist, all users can use cron, unless the file /etc/cron.deny exists, which lists the users that are not allowed to use cron12.
Reference: 1: Cron and Crontab usage and examples. 2: How to use cron in Linux.
Explanation:
The file /etc/cron.allow, if present, must contain all users that are allowed to use the cron scheduling system. This file is used to restrict the access to cron for security reasons. Only users listed in this file can create and edit their own crontab files using the crontab command. If the file does not exist, all users can use cron, unless the file /etc/cron.deny exists, which lists the users that are not allowed to use cron12.
Reference: 1: Cron and Crontab usage and examples. 2: How to use cron in Linux.
Question #28
Which of the following statements is true if the UID of a regular user is identical to the GID of a group?
- A . UID have precedence over GIDs, therefore the user is available while the group doesn’t.
- B . The user as well as the group are not available to avoid ambiguity due to the ID conflict.
- C . UIDs and GIDs are independent of each other, therefore the user as well as the group are still available.
- D . The user is the only member of the group, even if the group configuration contains other members.
- E . GIDs have precedence over UIDs, therefore the group is available while the user isn’t.
Correct Answer: C
C
Explanation:
UIDs and GIDs are two different types of identifiers for users and groups in Linux. They are not related to each other, and they do not affect each other’s availability or functionality. A user can have the same UID as another user’s GID, or vice versa, without any problem. The only restriction is that UIDs and GIDs must be unique within their own domain, i.e., no two users can have the same UID, and no two groups can have the same GID. Having the same UID as a GID does not imply any special
relationship between the user and the group, nor does it grant any extra permissions or access rights. The user and the group are still treated as separate entities by the system123
Reference: 1: Linux sysadmin basics: User account management with UIDs and GIDs 2: How to (Correctly) Change the UID and GID of a user/group in Linux 3: Linux File Permission: uid vs gid – CBT Nuggets
C
Explanation:
UIDs and GIDs are two different types of identifiers for users and groups in Linux. They are not related to each other, and they do not affect each other’s availability or functionality. A user can have the same UID as another user’s GID, or vice versa, without any problem. The only restriction is that UIDs and GIDs must be unique within their own domain, i.e., no two users can have the same UID, and no two groups can have the same GID. Having the same UID as a GID does not imply any special
relationship between the user and the group, nor does it grant any extra permissions or access rights. The user and the group are still treated as separate entities by the system123
Reference: 1: Linux sysadmin basics: User account management with UIDs and GIDs 2: How to (Correctly) Change the UID and GID of a user/group in Linux 3: Linux File Permission: uid vs gid – CBT Nuggets
Question #29
Which of the following is a legacy program provided by CUPS for sending files to the printer queues on the command line?
- A . lpd
- B . lpp
- C . lpq
- D . lpr
Correct Answer: D
D
Explanation:
The lpr command is a legacy program provided by CUPS for sending files to the printer queues on the command line. It is one of the Berkeley (lpr) printing commands that CUPS supports for compatibility with other Unix-like systems. The lpr command accepts one or more filenames as arguments and sends them to the default or specified printer. It also supports several options to control the printing process, such as the number of copies, the page size, the orientation, and the priority. The lpr command is equivalent to the lp command, which is one of the System V (lp) printing commands that CUPS also supports. However, the lp command has more options and features than the lpr command, and is recommended for use with CUPS.
Reference: Command-Line Printing and Options – CUPS
Command-Line Printer Administration – CUPS
Linux cups tutorial for beginners – Linux Tutorials – Learn Linux … CUPS Command-Line Utilities – Configuring and Managing … – Oracle
D
Explanation:
The lpr command is a legacy program provided by CUPS for sending files to the printer queues on the command line. It is one of the Berkeley (lpr) printing commands that CUPS supports for compatibility with other Unix-like systems. The lpr command accepts one or more filenames as arguments and sends them to the default or specified printer. It also supports several options to control the printing process, such as the number of copies, the page size, the orientation, and the priority. The lpr command is equivalent to the lp command, which is one of the System V (lp) printing commands that CUPS also supports. However, the lp command has more options and features than the lpr command, and is recommended for use with CUPS.
Reference: Command-Line Printing and Options – CUPS
Command-Line Printer Administration – CUPS
Linux cups tutorial for beginners – Linux Tutorials – Learn Linux … CUPS Command-Line Utilities – Configuring and Managing … – Oracle
Question #30
What is true regarding TCP port 23?
- A . Port 23 is the well known port for the telnet service which is a plain text protocol that should no longer be used.
- B . Port 23 is the well known port for the SSH service which provides secure logins.
- C . Port 23 is the well known port for the rlogin service which is SSL secured by default.
- D . Port 23 is the well known port for the system login services which are encrypted when the user runs the starttls command in his login shell.
Correct Answer: A
A
Explanation:
Port 23 is the well known port for the telnet service, which is a remote connection tool similar to SSH, but without the security of SSH. It uses a client/server model – a telnet client connects to a telnet server using TCP port 23. Due to lack of security, usage of telnet is discouraged in most situations, and firewalls routinely block port 23 to prevent incoming telnet connections. Port 23 is part of the topic 109.1: Fundamentals of internet protocols, which is one of the objectives of the LPI Linux Administrator – 102 exam12.
Reference: 1: https://learning.lpi.org/en/learning-materials/102-500/ 2: https://www.lpi.org/our-certifications/exam-102-objectives/
A
Explanation:
Port 23 is the well known port for the telnet service, which is a remote connection tool similar to SSH, but without the security of SSH. It uses a client/server model – a telnet client connects to a telnet server using TCP port 23. Due to lack of security, usage of telnet is discouraged in most situations, and firewalls routinely block port 23 to prevent incoming telnet connections. Port 23 is part of the topic 109.1: Fundamentals of internet protocols, which is one of the objectives of the LPI Linux Administrator – 102 exam12.
Reference: 1: https://learning.lpi.org/en/learning-materials/102-500/ 2: https://www.lpi.org/our-certifications/exam-102-objectives/