[libvirt] Libvirt/LXC (lxcControllerMain:380 : EPOLLHUP from fd 7)

[Daniel P. Berrange]

On Mon, Dec 07, 2009 at 03:02:53AM -0600, Tony Risinger wrote:
> hello,
> 
> i am trying to use libvirt with LXC, and having some issues...
> everything seems ok when using lxc-* tools.  host box is Arch Linux.
> ultimately i'm getting this error in the domain log:
> 
> .....
> 05:45:31.353: debug : lxcControllerMain:380 : EPOLLHUP from fd 7
> 
> i was getting this last night in #virt:
> 
> .....
> 20:49:57.545: error : lxcFdForward:230 : read of fd 7 failed: Input/output error
> libvir: Linux Container error : read of fd 7 failed: Input/output error

I believe this essentially says that the container has shutdown.

> -----CONFIGURATION
> 
> # host ptmx symlinked to pts/ptmx
> [root at PHS-001 vps]# ls -l /dev/ptmx
> lrwxrwxrwx 1 root root 8 2009-12-08 04:40 /dev/ptmx -> pts/ptmx
> 
> # guest ptmx symlinked to pts/ptmx
> [root at PHS-001 vps]# ls -l /vps/dom/ubuntu/root/dev/ptmx
> lrwxrwxrwx 1 root root 8 2009-12-06 04:11
> /vps/dom/ubuntu/root/dev/ptmx -> pts/ptmx

Avoid doing this - libvirt will set that up as part of the container
bootstrapping processs.

> # guest config...
> # i have tried the legacy <console type='pty' /> with same results
> # i dont fully understand this, why do i need to specify a host/source pty?
> [root at PHS-001 vps]# cat /vps/def/exec/sys/ubuntu.xml
> <domain type='lxc'>
>   <name>ubuntu</name>
>   <memory>500000</memory>
>   <os>
>     <type arch='i686'>exe</type>
>     <init>/sbin/init</init>
>   </os>
>   <clock offset='utc'/>
>   <on_poweroff>destroy</on_poweroff>
>   <on_reboot>restart</on_reboot>
>   <on_crash>destroy</on_crash>
>   <devices>
>     <filesystem type='mount'>
>       <source dir='/vps/dom/ubuntu/root'/>
>       <target dir='/'/>
>     </filesystem>
>     <console type='pty'>
>       <source path='/dev/pts/4'/>

Leave out the <source> here - that's auto-generated when the container
starts

>       <target port='0'/>
>     </console>
>   </devices>
> </domain>
> 
> -----PROCEDURE
> 
> [root at PHS-001 vps]# LIBVIRT_DEBUG=1 libvirtd --daemon
> 05:42:46.121: debug : virInitialize:278 : register drivers
> .....
> 
> [root at PHS-001 vps]# virsh -c lxc:/// define /vps/def/exec/sys/ubuntu.xml
> Domain ubuntu defined from /vps/def/exec/sys/ubuntu.xml
> 
> [root at PHS-001 vps]# virsh -c lxc:/// define /vps/def/exec/sys/ubuntu.xml
> Domain ubuntu defined from /vps/def/exec/sys/ubuntu.xml
> 
> [root at PHS-001 vps]# virsh -c lxc:/// start ubuntu
> Domain ubuntu started
> 
> [root at PHS-001 vps]# virsh -c lxc:/// console ubuntu
> error: Unable to get domain status
> error: internal error Unable to get cgroup for ubuntu




> 
> -----LOGS
> 
> # /var/log/libvirt/lxc/ubuntu.log
> 05:45:31.126: debug : virCgroupMakeGroup:450 : Make group /libvirt/lxc
> 05:45:31.126: debug : virCgroupMakeGroup:462 : Make controller
> /cgroup/1534/libvirt/lxc/
> 05:45:31.211: debug : lxcContainerStart:832 : clone() returned, 1536
> 05:45:31.353: debug : lxcControllerMain:380 : EPOLLHUP from fd 7


> 
> i've tried endless variations of the <devices> section, but i just
> cant seem to get anything going with libvirt/LXC once i move the root
> to a new location for a system container.  same container works fine
> with lxc-* tools (although i manually make a bridge).  any help is
> appreciated,

Rather that going straight for a full OS, try just setting up a trivial
busybox root environment which just takes you intoa busybox shell.

eg, in /sbin/init just have

   #!/sbin/busybox

   sh

(Obviously install busybox in /sbin inside the root env too :-)

Daniel
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