Wiki source code of Openwrt Boot Notes
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| author | version | line-number | content |
|---|---|---|---|
| 1 | |||
| 2 | |||
| 3 | = initramfs-kernel = | ||
| 4 | |||
| 5 | kernel runs /init. | ||
| 6 | |||
| 7 | /init is a script which sets INITRAMFS=1 and then execs /sbin/init. | ||
| 8 | |||
| 9 | /sbin/init is ELF comes from procd package. What it does (as pid=1): | ||
| 10 | |||
| 11 | * early (different from procd early): | ||
| 12 | ** mount /proc, /sysfs, and create /dev nodes, create /tmp subdirs etc | ||
| 13 | ** set PATH | ||
| 14 | * kmodloader in subprocess (waits until done) | ||
| 15 | * preinit | ||
| 16 | ** plugd in subprocess (seem to deal with firmware) | ||
| 17 | ** /etc/preinit in subprocess | ||
| 18 | * when /etc/preinit is done then it execvp the "real" /sbin/procd | ||
| 19 | |||
| 20 | |||
| 21 | |||
| 22 | procd states: | ||
| 23 | |||
| 24 | * early (first state): | ||
| 25 | ** coldplug (remount /dev, etc) | ||
| 26 | *** start udevtrigger in subproc | ||
| 27 | *** when udevtrigger completes, hotplug | ||
| 28 | *** when hotplug completes, next state (ubus) | ||
| 29 | * ubus: | ||
| 30 | ** start attempts to connect to ubs | ||
| 31 | ** start ubus as service | ||
| 32 | ** once connection's done then next state (init) | ||
| 33 | * init - read /etc/inittab and run: | ||
| 34 | ** respawn - things that need to keep rerunning once quitted | ||
| 35 | ** askconsole | ||
| 36 | ** askfirst - the "Press Enter to activate this console" message | ||
| 37 | ** sysinit - (usually /etc/init.d/rcS with S) and then next state (running) | ||
| 38 | * running - waits for shutdown signal (usr1/usr2) or reboot (int/term) | ||
| 39 | * shutdown | ||
| 40 | ** runs shutdown command per inittab (also /etc/init.d/rcS but with K) | ||
| 41 | ** when done next state (halt) | ||
| 42 | * halt - kill everything and either enter sleep loop or reboots | ||
| 43 | |||
| 44 |