Basic of Systemd

Lets Talk about systemd

Name: Praveen Kumar

Contact: kumarpraveen [AT] fedoraproject DOT org

Date: 2015-07-11

1

Agenda

• What is systemd

• What capabilities it provides

• How to use systemd

• How a service file looks like

• Intro about systemd-nspawn

• Resources

Agenda

2

What is systemd

• Modular

• Asynchronous and concurrent

• Create snapshot

• features a fully language-agnostic API

... Much more

What is systemd

3

systemd Cont...

systemd Cont...

4

How to use systemd

• Default init system for CentOS

• List out units

• systemctl list-units

• List out services

• systemctl list-units --type service

• systemctl list-units --type service --all

How to use systemd

5

• systemctl list-unit-files --type=service

• ls /usr/lib/systemd/system/*.wants

How to use systemd

6

How to use systemd cont...

• List out targets

• systemctl list-units --type targets

• Check CGroup tree

• systemd-cgls

How to use systemd cont...

7

Service file Template

[Unit]Description=The Apache HTTP ServerAfter=network.target remote-fs.target nss-lookup.target

[Service]Type=notifyEnvironment=LANG=CExecStart=/usr/sbin/httpd $OPTIONS -DFOREGROUNDExecReload=/usr/sbin/httpd $OPTIONS -k graceful


9

# Send SIGWINCH for graceful stopKillSignal=SIGWINCHKillMode=mixedPrivateTmp=true

[Install]WantedBy=multi-user.target


10

systemd snapshot

• Crate a snapshot of existing unit config

$ sudo systemctl snapshot test$ sudo systemctl -all list-units | grep test$ sudo systemctl show test$ sudo systemctl isolate test.snapshot$ sudo systemctl delete test

systemd snapshot

11

sysemd-nspawn

• systemd-nspawn is a small utility which is use to create light weightcontainers

• Setup a container

$ sudo yum -y --nogpg --releasever=7 --installroot=/srv/mycontainer \install systemd passwd yum vim-minimal

sysemd-nspawn

12

sysemd-nspawn cont...

• Setup container password

$ sudo systemd-nspawn -D /srv/mycontainer

• Start a container

$ sudo systemd-nspawn -jbD /srv/mycontainer

sysemd-nspawn cont...

13

Resources

• http://www.freedesktop.org/wiki/Software/systemd

• http://linux.xvx.cz/2014/06/systemd-cheatsheet.html

Resources

14

http://www.freedesktop.org/wiki/Software/systemd

http://linux.xvx.cz/2014/06/systemd-cheatsheet.html

Thank You

Thank You

15