[libvirt] simple LXC/libvirt busybox container (Unable to get cgroup)

[Tony Risinger]

i'm trying to get even the simplest busybox container with libvirt+LXC
with very limited success.  I feel l am missing something supremely
simple for me to be hung on this for weeks.

i dont see anything interesting in domain log, but getting this error
from "LIBVIRT_DEBUG=1 libvirtd":

05:27:56.113: error : lxcDomainGetInfo:462 : internal error Unable to
get cgroup for arch-nano
05:27:56.113: debug : virDomainFree:2004 : domain=0x81d8e68
05:27:56.113: debug : virUnrefDomain:422 : unref domain 0x81d8e68 arch-nano 1
05:27:56.113: debug : virReleaseDomain:376 : release domain 0x81d8e68 arch-nano
05:27:56.113: debug : virReleaseDomain:392 : unref connection 0x81dc0f0 2
05:27:56.113: debug : remoteSerializeError:141 : prog=536903814 ver=1
proc=16 type=1 serial=4, msg=internal error Unable to get cgroup for
arch-nano

i've been using this root filesystem layout:

[root at PHS-001 arch-nano]# tree
.
|-- bin
|   |-- cat -> ../sbin/busybox
|   |-- chdir -> ../sbin/busybox
|   |-- chmod -> ../sbin/busybox
|   |-- ls -> ../sbin/busybox
|   |-- rm -> ../sbin/busybox
|   |-- sh -> ../sbin/busybox
|   `-- vi -> ../sbin/busybox
|-- dev
|   `-- pts
|-- etc
|-- proc
|-- sbin
|   |-- busybox
|   `-- init -> busybox
`-- sys

all folders besides /bin and /sbin were created by libvirt.  i tried
using the /sbin/init script previously suggested:

#!/sbin/busybox
sh

but i get a similar results either way (script/symlink):

 8173 ?        Ss     0:00 /usr/lib/libvirt-git/libvirt_lxc --name
arch-nano --console 11 --background
 8175 pts/0    Ss+    0:00 init
 8177 ?        Ss     0:00 init
 8181 ?        Zs     0:00 [init] <defunct>
 8182 ?        Zs     0:00 [init] <defunct>
 8183 ?        Zs     0:00 [init] <defunct>


"busybox init" doc says that without an /etc/inittab, sh will be
started on /dev/tty2... im am using this config:

<domain type='lxc'>
  <name>arch-nano</name>
  <memory>500000</memory>
  <os>
    <type>exe</type>
    <init>/sbin/init</init>
  </os>
  <devices>
    <filesystem type='mount'>
      <source dir='/vps/dom/arch-nano'/>
      <target dir='/'/>
    </filesystem>
  </devices>
</domain>

on this config i tried removing the console/serial section altogether,
but i attempted many configurations of serial/console, including
changing the <target> to "2", in attempt to match busybox default.

[root at PHS-001 arch-nano]# virsh -c lxc:/// console arch-nano
error: Unable to get domain status
error: internal error Unable to get cgroup for arch-nano

[root at PHS-001 arch-nano]# mount | grep cgroup
none on /cgroup type cgroup (rw)

if anyone can please point out what i am doing wrong to not be able to
move the root and get a console, i'd greatly appreciate it.  ive been
really stuck on this; i'd rather not write a bunch of scripts/wrappers
for lxc-* tools when libvirt does it all splendidly already!

libvirt 0.7.4+
kernel 2.6.32 (am i missing a CONFIG_*?)

thanks for your time