[uml-user] reboot guest OS ??? is it possible ?

[<mr...@fr...>]

Hello all,

I recently investigate on UML, and i have a little issue with the way system
reboots. (btw i dont know if this the way to go *really*)

My config is for host: debian jessie out of the box..
for guest OS i try several kernel and filesytstem but both hangs with the same
issues:
FS1 : debootstraped fs from Debian jessie
FS2 : devloop.org.uk filesystem Debian jessie.

Kernel1: 3.16 custom compiled kernel (.config from devloop.uk.org)
Kernel2: linux.uml debian kernel from package user-mode-linux
Kernel3: compiled devloop.uk.org kernel 3.18

if i launch 1 station and reboot from the guest OS shell, i saw on the host a
uml_watchdog process that seems to kill my guest OS few seconds after...

I cant find any documentation concerning this uml_watchdog, can't figure out how
it spawn from guest OS reboot...

but i am quite sure it is the culprit since copying /bin/true
to /usr/bin/uml_watchdog solve the issue... however i still have defunct process
(ex uml_watchdog).

The source of this uml_watchdog.c i found on internet doesnt make me much sense
since it looks like just looking from input on stdin ?.

Btw UML Watchdog timer is enabled on the guest OS.. not sure it is correctly
running since the quest OS complains about error on device 130 which is
/dev/watchdog

Does anyone have clue about uml_watchdog ???

I definitively think reboot somewhere else from uml_mconsole is a *BAD* idea....

more coming....


Trying to share the same root filesystem on 2 UML:

linux.uml ubda=/tmp/m1.cow,./filesystem mem=256M con0=fd:0,fd:1 con=null
linux.uml ubda=/tmp/m2.cow,./filesystem mem=256M con0=fd:0,fd:1 con=null


if i launch these 2 stations and reboot them from shell at the same time, one
hang, the other reboot fine.

and as usual it looks ok if i do this from uml_mconsole xxx reboot .

The bad news is that i would like to give user the opportunity to rebbot a guest
OS without giving access to the host....

Any help greatly apprciated, since i spend much time trying to debug this issue.
I can still do further investigation...

Thx