finit/doc/bootstrap.md

Bootstrap

1. Populate /dev
2. Parse /etc/finit.conf
3. Load all .so plugins
4. Remount/Pivot / to get R+W
5. Call 1st level hooks, HOOK_ROOTFS_UP
6. Mount /etc/fstab and swap, if available
7. Cleanup stale files from /tmp/* et al
8. Enable SysV init signals
9. Call 2nd level hooks, HOOK_BASEFS_UP
10. Start all 'S' runlevel tasks and services
11. Load kernel params from /etc/sysctl.d/*.conf, /etc/sysctl.conf et al. (Supports all locations that SysV init does.)
12. Set hostname and bring up loopback interface
13. Call network script, if set in /etc/finit.conf
14. Call 3rd level hooks, HOOK_NETWORK_UP
15. Switch to the configured runlevel from /etc/finit.conf, default 2. At every runlevel change all *.conf files in /etc/finit.d/ are (re)loaded and new services, tasks, and blocking run commands are started. Provided they are allowed in the new runlevel and all of their conditions, if any, are set.
16. Call 4th level hooks, HOOK_SVC_UP
17. If runparts <DIR> is set, run-parts(8) is called on <DIR>
18. Call /etc/rc.local, if it exists and is an executable shell script
19. Call 5th level (last) hooks, HOOK_SYSTEM_UP
20. Start TTYs defined in /etc/finit.conf, or rescue on /dev/console

In (10) and (15) tasks and services defined in /etc/finit.conf are started. Remember, all service and task stanzas are started in parallel and run in sequence, and in the order listed. Hence, to emulate a SysV /etc/init.d/rcS one could write a long file with only run statements.

Notice the five hook points that are called at various point in the bootstrap process. This is where plugins can extend the boot in any way they please.

For instance, at HOOK_BASEFS_UP a plugin could read an XML file from a USB stick, convert/copy its contents to the system's /etc/ directory, well before all 'S' runlevel tasks are started. This could be used with system images that are created read-only and all configuration is stored on external media.