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Init systems

Run Levels​

  • A system's run level (aka init state) defines what services and resources are available to users

  • A system can be in only one run level at a time

  • Most common run levels

    • Run level 3:

      • All system resources are available and users can login
      • Booting a system brings it to run level 3
      • Day-to-day operations

    • Run level 6:

      • Stop the OS and reboots to the state that is defined by initdefault in /etc/inittab

    • Run level 0:

      • Shutdown, safe to turn off power

sysvinit​

  • /etc/init.d is a folder containing initialization and termination scripts for changing init states
  • The boot order is determined during boot by the order of files in /etc/rc?.d
tip

insserv update-rc.d

systemd​

  • System Daemon starts the system services in parallel, speeds up the initialization process

  • GUI:

    • Cockpit
      • Login as root: Remove root from /etc/cockpit/disallowed-users. Issue
      • Available at 9090 port

WSL meets systemd​

  • WSL must be 0.67.6 or newer
  • Open WSL distro
  • Edit wsl.conf
/etc/wsl.conf
[boot]
systemd=true
  • Restart WSL
wsl.exe --shutdown