Systemd

What is Systemd?

What is init system?

• SysV
• upstart
• launchd

Why do we need another init system?

https://github.com/puma/puma/blob/master/tools/jungle/init.d/puma

Welcome Systemd

https://github.com/monterail/ansible-puma/blob/master/templates/puma.service.j2

Why should I care?

• Debian
• Ubuntu
• CentOS
• Fedora
• Arch
• CoreOS
• OpenSUSE
• Mageia

We use it too

What I have to know?

Design

• service
• target
• timer
• ...

/etc/systemd/system

/lib/systemd/system

systemctl

systemctl status
systemctl status myapp
systemctl restart myapp
systemctl reload myapp
systemctl start myapp
systemctl stop myapp
systemctl enable myapp
systemctl disable myapp
systemctl --failed

journalctl

journalctl -f # like tail -f
journalctl -u unitname
journalctl -b # since last boot
journalctl -n 100
journalctl --since yesterday
journalctl -o json # different outputs
journalctl -p 3..6 # filtering by priority

Templates

[Unit]
Description=%I Sidekiq Daemon
Documentation=https://github.com/monterail/ansible-sidekiq
StopWhenUnneeded=yes
PartOf=%i.target

[Service]
User=%i
WorkingDirectory=/home/%i/app/current
ExecStart=/bin/bash -lc './bin/sidekiq -C ./config/sidekiq.yml'
EnvironmentFile=/home/%i/.env
Restart=always
KillMode=process
Type=simple

/etc/systemd/system/sidekiq@.service

systemctl enable sidekiq@myapp.service

root@development:~# ls -l /etc/systemd/system/tailored_core.target.wants/
total 0
... core-coordinator.service -> /etc/systemd/system/core-coordinator.service
... sidekiq@tailored_core.service -> /etc/systemd/system/sidekiq@.service
... unicorn@tailored_core.service -> /etc/systemd/system/unicorn@.service

https://github.com/monterail/ops/wiki/Knowledge-Base#systemd

Demo and bye