On Sun, 2010-01-31 at 13:38 -0600, Tony Risinger wrote:
On Sat, Jan 30, 2010 at 12:11 PM, Michael H. Warfield m...@wittsend.com
wrote:
On Sat, 2010-01-30 at 14:20 +0100, Dominik Schulz wrote:
Hi,
I'm fairly new to LXC and I am looking for a way to execute a command
inside a
running container (a full blow one with its own rootfs and full isolation).
lxc-execute doesn't seem to do the trick and lxc-console requires
credential
to login. I'm looking for a way to execute command w/o having to login via
ssh
or the lxc-console, so I can execute command directly inside the
containers to
shut them down properly.
This is being worked on and looked at now through the use of some sort
of daemon in the running container but is not currently possible. More
over, cgroups in the kernel does not currently support joining an active
cgroup, and may never support it, so it would have to be done through
the mediation of some sort of daemon in the running container and
communicating with the host. There's been discussion on the -devel list
over the optimal way to do it and there are some patches running around
but AFAICT nothing has really been committed or committed to at this
time.
if your using the standard init program, and you are only trying to
control stutdown/reboot, i use something like this in my container
inittab:
p6::ctrlaltdel:/sbin/init 6
p0::powerfail:/sbin/init 0
ctrlaltdel responds to a SIGINT, and powerfail responds to SIGPWR.
this lets you send a:
kill -INT init pid
to reboot, and:
kill -PWR init pid
Ah that's a nice trick. I'll have to incorporate that into my scripts.
to shutdown. you will also need the help of a monitor process to
overcome the fact that the init process will hang around, even though
all other processes in the container are dead. an earlier thread
detailed a nice trick using inotifywait and the utmp file in the
container, see this thread for ideas:
http://www.mail-archive.com/lxc-users@lists.sourceforge.net/msg00040.html
specifically this post on:
http://www.mail-archive.com/lxc-users@lists.sourceforge.net/msg00049.html
you basically monitor the utmp file in the container for a change,
then run runlevel utmp file to get the runlevel in the container,
and act appropriately. here is an excerpt from my scripts (originally
based off one provided in the previous thread), it has variables
specific to my setup but it's fairly self explanatory:
while true; do
# time of 5 minutes on it JUST IN CASE...
vps_utmp=${VPS_DOM}/${vps}/rootfs/var/run/utmp
inotifywait -qqt 300 ${vps_utmp}
if [ $(wc -l ${VPS_VAR}/cgroup/${vps}/tasks) -eq 1 ]; then
runlevel=$(runlevel ${vps_utmp})
case $runlevel in
N*)
# nothing for new boot state
;;
??0)
# halted... kill vps.
lxc-stop -n ${vps}
break
;;
??6)
# rebooting... kill vps and start again...
lxc-stop -n ${vps}
lxc-wait -n ${vps} -s STOPPED
lxc-start -d -n ${vps} -o ${VPS_LOG}/${vps}.log
# loop again.
;;
*)
# make sure vps is still running
state=$(lxc-info -n ${vps} | sed -e 's/.* is //')
[ $state = RUNNING ] || break
;;
esac
fi
done
Yeah, that's some of my stuff. I've since rolled that into an lxc-run
script that does some initialization and then forks off a subprocess
that calls lxc_start as a daemon and then drops into a variation of that
loop. I'll probably be posting that script in the next day or so. I'm
almost done cleaning up some of the OpenVZ migration hacks that are
incorporated into it.
Mike
--
Michael H. Warfield (AI4NB) | (770) 985-6132 | m...@wittsend.com
/\/\|=mhw=|\/\/ | (678) 463-0932 | http://www.wittsend.com/mhw/
NIC whois: MHW9 | An optimist believes we live in the best of all
PGP Key: 0x674627FF| possible worlds. A pessimist is sure of it!
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