Boot steps

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VyOS 1.20+ uses Debian Jessie as the base Linux operating system. Jessie was the first version of Debian that uses systemd as the default init system.

These are the boot steps for VyOS 1.2.0+

  1. The BIOS loads Grub (or isolinux for the Live CD)
  2. Grub then starts the Linux boot and loads the Linux Kernel (/boot/vmlinuz)
  3. Kernel Launches Systemd (/lib/systemd/systemd)
  4. Systemd loads the VyOS service file (/lib/systemd/system/vyos-router.service)
  5. The service file launches the VyOS router init script (/usr/libexec/vyos/init/vyos-router - this is part of the vyatta-cfg Debian package)
    1. Starts FRR - successor to GNU Zebra and Quagga
    2. Initialises the boot configuration file - copies over config.boot.default if there is no configuration
    3. Runs the configuration migration, if the configuration is for an older version of VyOS
    4. Runs The pre-config script, if there is one (/config/scripts/vyos-preconfig-bootup.script)
    5. If the config file was upgraded, runs any post upgrade scripts (/config/scripts/post-upgrade.d)
    6. Starts rl-system and firewall
    7. Mounts the /boot partition
    8. The boot configuration file is then applied by (/opt/vyatta/sbin/vyatta-boot-config-loader /opt/vyatta/etc/config/config.boot)
      1. The config loader script writes log entries to /var/log/vyatta-config-loader.log
    9. Runs telinit q to tell the init system to reload /etc/inittab
    10. Finally it runs the post-config script (/config/scripts/vyos-postconfig-bootup.script)