Systemd is used to manage the boot process and startup of Linux systems. It aims to boot the system faster by running startup tasks in parallel rather than sequentially. The main commands to interact with Systemd are systemctl to manage units/services, systemd-analyze to analyze the boot process duration and components, and the configuration files are located in /etc/systemd and /usr/lib/systemd/system.

1. Systemd

2. Systemd
• Systemd makes a server boot quicker because it uses fewer scripts
and tries to run more tasks in parallel
• Systemd calls them units (to get a better understanding about the
problems Systemd solves
• The global Systemd configuration is stored in
the /etc/systemd directory.
• Service configuration files are located in
the /usr/lib/systemd/system directory.

3. • To get the current release of Systemd, type:

4. Boot Process
• Systemd primary task is to manage the boot process and provides
information about it.
To get the boot process duration, type
Systemd-analyze
• To get the time spent by each task during the boot process, type:
Systemd-analyze blame

5. • To get the list of the critical chain of tasks during the boot process
(any additional delay of these tasks would cause an increase of the
overall boot time), type:
Systemd-analyze critical-chain

6. systemctl and systemd units
• The systemctl command is used to manage different types of systemd
objects, called units.
• A list of available unit types can be displayed with systemctl - t help

7. • Query the state of all units to verify a system startup
systemctl
Query the state of only the service units.
systemctl --type=service
The status argument may also be used to determine if a particular unit
is active and show if the unit is enabled to start at boot time
systemctl is-active sshd.service
systemctl is-enabled sshd.service

8. • List the active state of all loaded units. Optionally, limit the type of
unit.
• The --all option will add inactive units
systemctl list-units --type=service
systemctl list-units --type=service --all