Wiki source code of Openwrt Notes

Version 6.1 by Leon Poon on 2019/01/06 08:47
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2
3 = initramfs-kernel =
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5 kernel runs /init.
6
7 /init is a script which sets INITRAMFS=1 and then execs /sbin/init.
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9 /sbin/init is ELF comes from procd package. What it does (as pid=1):
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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
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20 procd states:
21
22 * early (first state):
23 ** coldplug (remount /dev, etc)
24 *** start udevtrigger in subproc
25 *** when udevtrigger completes, hotplug
26 *** when hotplug completes, next state (ubus)
27 * ubus:
28 ** start attempts to connect to ubs
29 ** start ubus as service
30 ** once connection's done then next state (init)
31 * init - read /etc/inittab and run:
32 ** respawn - things that need to keep rerunning once quitted
33 ** askconsole
34 ** askfirst - the "Press Enter to activate this console" message
35 ** sysinit - (usually /etc/init.d/rcS with S) and then next state (running)
36 * running - waits for shutdown signal (usr1/usr2) or reboot (int/term)
37 * shutdown
38 ** runs shutdown command per inittab (also /etc/init.d/rcS but with K)
39 ** when done next state (halt)
40 * halt - kill everything and either enter sleep loop or reboots
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43
44 = Debian =
45
46 Needs devtmpfs in kernel. This seem to be first thing that /sbin/init does. (Maybe systemd specific.)
47
48 {{code}}
49 mkdir -pv /mnt/debian && mknod /dev/sda b 8 0 && cryptsetup open /dev/sda usb && vgchange -ay vol_grp1 && mount /dev/vol_grp1/logical_vol1 /mnt/debian
50 exec switch_root /mnt/debian /sbin/init
51 {{/code}}