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Systemd Init System

Aug 3, 2019
Apr 22, 2020

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D-BUS
Desktop Bus
S/w bus for communication b/w processes using IPC and RPC
D-bus wire protocol allows connection b/w various processes using unix domain sockets
:1.1557 unique process address

How to configure network using systemd?

systemd uses networkd to configure netwrok interfaces.

Configuration file path /etc/systemd/network/dhcp.network

  • init system for linux
  • System and service Manager
    • runs PID 1
    • Replaces runlevels
    • controls machine boot
    • recplaces lots of shell scripts for system boot
  • Software platform for developing other apps
  • Glue between user and kernel spacce applications
  • Resources are called Units, it manages them in dependency graph.

  • Seperate bootstrap scripts one-shot applications on various cloud environments.

    [Match]
Name=en*

[Network]
Address=192.168.0.15/24
Gateway=192.168.0.1
# OR
DHCP=yes
notify-send
send alerts from terminal commands/scripts

Timedate control

systemd manages timesyncd daemon which requires linux user and group by name systemd-timesync to be present on system. It synchronizes system clock across the network

timedatectl list-timezones
set system time and zone settings
timedatectl status
/var/lib/systemd/clock

This file contains the timestamp of the last successful synchronization.

systemctl status systemd-timedated.service
bat /lib/systemd/system/systemd-timedated.service

localectl
timedatectl status

Disable timwsyncd service in yocto

To disable timesyncd in your Yocto build, create a *.bbappend recipe in your own layer called

recipes-core/systemd/systemd_216.bbappend
And add the following content

PACKAGECONFIG[timesyncd] = "--enable-timesyncd,--disable-timesyncd,timesyncd"

PACKAGECONFIG_remove = "timesyncd"

Systemd vs Supervisord

Let’s say I have a Django application named Foo. I want to be sure Foo is running all the time, even if it crashes. Also, I want a simple interface to start, stop and restart its process. Supervisord is a perfect match for this job.

  • Process Monitoring
  • systemd has not, like controlling services with a web interface
  • Project Cockpit1 interactive server admin interface

Cockpit uses systemd and the DBus APIs it provides to configure and monitor core aspects of the system.

[Unit] Description="Foo web application" After=network.target [Service] User=foo Group=foo Environment=LANG=en_US.UTF-8,LC_ALL=en_US.UTF-8 ExecStart=/home/foo/bin/start_foo [Install] WantedBy=multi-user.target

LC_ALL: cannot change locale

sudo locale-check
sudo locale -a
sudo locale-gen en_US
sudo update-locale LANG=en_US

Footnotes

  1. Project cockpit [return]