==================
Understand systemd
==================

Systemd
=======

.. image:: images/systemd001.png

Framework
*********

.. image:: images/systemd002.png

Basic Command
*************
syntax
------
list units::

    $ systemctl list-units
    $ systemctl list-units --all
	$ systemctl list-units --type service --all

start/stop service::

	# systemctl start [name.service]
	# systemctl stop [name.service]
	# systemctl restart [name.service]
	# systemctl reload [name.service]
	$ systemctl status [name.service]
	# systemctl is-active [name.service]



Service List 
------------

    * Service: Linux Service
    * Target: group of units
    * Automount: filesystem auto-mountpoint
    * Device: kernel device names, which you can see in sysfs and udev
    * Mount: filesystem mountpoint
    * Path: file or directory
    * Scope: external processes not started by systemd
    * Slice: a management unit of processes
    * Snapshot: systemd saved state
    * Socket: IPC (inter-process communication) socket
    * Swap: swap file
    * Timer: systemd timer.

Test
----
::

	sudo su -
    dnf install httpd
    systemctl start httpd.service
         -- หรือ --
    systemctl start httpd.service
    systemctl enable httpd.service
   
Unit Detail
------------
::

	systemctl cat httpd
    systemctl list-dependencies httpd

Dependencies
------------
::

  	systemctl list-dependencies sshd.service


Checking Unit Properties
------------------------
::

	systemctl show sshd.service
  

Masking and Unmasking Units
---------------------------
::

	systemctl mask httpd
    systemctl start httpd
    systemctl unmask httpd
    systemctl start httpd