Chapter 9 Daemons

Question 1

What command shows you the status of the service?

Answer 1

systemctl status ssh.service

Question 2

What are daemons in the context of Linux?

Answer 2

Processes that belong to the system or a service, start at bootup, and run in the background

Daemons affect all users and typically end with the letter ‘d’, as in systemd.

Question 3

What is the first process upon bootup in Linux?

Answer 3

systemd

Systemd has a PID of 1 and manages various types of units.

Question 4

Name the three types of units managed by systemd.

Answer 4

• Services
• Sockets
• Paths

Services function as web servers, sockets handle communication, and paths relate to files.

Question 5

What command is used to control systemd?

Answer 5

systemctl

This command allows users to manage services sockets and paths

Question 6

How do you show only active services using systemctl?

Answer 6

$systemctl list-units –type=service

This command filters the output to display only active services.

Question 7

What command checks if a service is active?

Answer 7

$systemctl is-active sshd.service

This command returns the active status of the specified service.

Question 8

To start a stopped service, which command would you use?

Answer 8

$sudo systemctl start sshd.service

This command initiates the specified service.

Question 9

What command stops an active service?

Answer 9

$sudo systemctl stop sshd.service

This command halts the specified service.

Question 10

If you make configuration changes to a service, what command do you use to restart it?

Answer 10

$sudo systemctl restart sshd.service

Restarting the service loads the new configuration into memory.

Question 11

What command is used to reload a service without changing its PID?

Answer 11

$sudo systemctl reload sshd.service

This command allows the service to load new information without a full restart.

Question 12

How can you view the dependencies for a service?

Answer 12

$sudo systemctl list-dependencies sshd.service

This command shows the files required for the service to run.

Question 13

What does masking a service do?

Answer 13

Prevents a service from accidentally being started

Use $sudo systemctl mask sshd.service to mask and $sudo systemctl unmask sshd.service to unmask.

Question 14

To enable a service to start automatically at bootup, which command is used?

Answer 14

$sudo systemctl enable sshd.service

This command sets the service to launch automatically upon system startup. can do same thing for disabling.

Question 15

Fill in the blank: In Linux, just because an application is installed doesn’t mean it is _______.

Answer 15

running

You must start and enable the service for it to be available for use.