@yifanlu:
Yep, that's it
.
Here's the runlevel breakdown on a K3:
rcS is the low level boot runlevel
rc0 is the shutdown runlevel
rc1 is the single user runlevel (probably useless/broken on a Kindle)
rc2 is the diagnostic runlevel
rc3 is the updater runlevel
rc4 is the reboot diagnostic runlevel
rc5 is the boot (framework) runlevel
rc6 is the reboot runlevel
So, yeah, we're usually on rc5, the update process switches to rc3, and goes back to rc5 once it's done (and when the update script doesn't trigger a reboot, like official updates with kernel updates, in which case it just goes from rc3 to reboot. The 3.x updates are even weirder, they drop a temporary init script early during rc5 that'll call otaup from there, and reboot [ie. that's why there's been a shitload of reboots needed for every 3.x official updates]).