I run an Embedded Linux system, which is created with Buildroot 2021.02.2 and has BusyBox v1.33.0, Linux 5.4.8, glibc 2.32.
When I run
# reboot
It does nothing, and there is no error or warning in syslog.
However, when I run with -f force option, it reboots the device.
# reboot --help
BusyBox v1.33.0 () multi-call binary.
Usage: reboot [-d DELAY] [-nf]
Reboot the system
-d SEC Delay interval
-n Do not sync
-f Force (don't go through init)
# reboot -f
< reboots OK >
I have debug messages in /etc/init.d/rcK and in inittab, but it looks like the execution after reboot is not reaching the inittab nor rcK.
The "shutdown" part of /etc/inittab:
# Stuff to do before rebooting
::shutdown:/bin/echo "MY DEBUG" | /usr/bin/logger
::shutdown:/etc/init.d/rcK
::shutdown:/sbin/swapoff -a
::shutdown:/bin/umount -a -r
::respawn:/usr/bin/monit -Ic /etc/monitrc
I have confirmed the libc.so has the reboot functionality:
nm build/glibc-2.32-37-g760e1d287825fa91d4d5a0cc921340c740d803e2/build/libc.so.6 | grep reboot
000cb2e0 T reboot
This makes me think there is a mistake in the communication with init. The system has Busybox init: BR2_INIT_BUSYBOX=y.
Signals accepted by init:
# init --help
BusyBox v1.33.0 () multi-call binary.
Usage: init
Init is the first process started during boot. It never exits.
It (re)spawns children according to /etc/inittab.
Signals:
HUP: reload /etc/inittab
TSTP: stop respawning until CONT
QUIT: re-exec another init
USR1/TERM/USR2/INT: run halt/reboot/poweroff/Ctrl-Alt-Del script
Do you have any ideas how to debug this situation? I want the reboot to work with proper shutdown and without having to omit the init.
EDIT:
The reboot command from busybox sometimes has effect, and sometimes not, this is why this case is especially confusing.
When it works, it gives the following log in syslog:
Jan 1 00:20:26 : starting pid 494, tty '': '/etc/init.d/rcK'
Jan 1 00:20:26 [my_service: signal_handler] MyService terminated
Jan 1 00:20:26 bluetoothd[368]: Terminating
Jan 1 00:20:26 bluetoothd[368]: Stopping SDP server
Jan 1 00:20:26 bluetoothd[368]: Exit
Jan 1 00:20:27 dropbear[346]: Early exit: Terminated by signal
Jan 1 00:20:27 ntpd[318]: ntpd exiting on signal 15 (Terminated)
Jan 1 00:20:28 ModemManager[312]: <info> caught signal, shutting down...
Jan 1 00:20:28 ModemManager[312]: <info> ModemManager is shut down
Jan 1 00:20:29 syslog-ng[236]: syslog-ng shutting down; version='3.30.1'
Jan 1 00:20:29 : starting pid 575, tty '': '/sbin/swapoff -a'
Jan 1 00:20:29 : starting pid 576, tty '': '/bin/umount -a -r'
When it has no effect, there is no evidence in logs, not even calling the rcK. Do you have ideas what could be the reason for such behavior? As a last resort, I can move to SysVinit if this would solve the problem.
EDIT: SOLUTION
Posting the solution here since the question was closed.
When writing init scripts, always use start-stop-daemon with either -b -m -p, or with just -p.
Using -m without -b option can cause problems similar to the one described in question.
Examples of good usage:
start-stop-daemon -S -q -m -b -p /var/run/logrotate.pid --exec /usr/sbin/logrotate.sh
or
start-stop-daemon -S -q -p "$PIDFILE" -x "/usr/sbin/$DAEMON"
More info: