[libvirt-users] Getting IP address of a lxc container via libvirt

[Lars Kellogg-Stedman]

On Sat, Dec 19, 2015 at 12:13:07AM +0530, Harish Vishwanath wrote:
> Hello
> 
> I wanted to understand if there is a way to get LXC container's ip address.
> 
> - virDomainInterfaceAddresses API only works for qemu/kvm and not with the
> lxc driver.
> 
> What other options do I have?

If you're not looking for a libvirt-only solution, you can just use
`nsenter`:

    nsenter -t <pid-inside-container> -n ifconfig

> virsh -c lxc:/// lxc-enter-namespace <domain> --noseclabel /sbin/ifconfig
> libvirt:  error : Expected at least one file descriptor

For what it's worth, I was able to do the above without a problem with
Fedora 23, running an alpine linux container (just unpacked the alpine
docker image):

  sudo virsh -c lxc:/// lxc-enter-namespace alpine -- /sbin/ifconfig eth0
  eth0      Link encap:Ethernet  HWaddr 00:16:3E:10:25:32  
            inet addr:192.168.124.4  Bcast:192.168.124.255  Mask:255.255.255.0
            UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
            RX packets:46 errors:0 dropped:0 overruns:0 frame:0
            TX packets:9 errors:0 dropped:0 overruns:0 carrier:0
            collisions:0 txqueuelen:1000 
            RX bytes:4034 (3.9 KiB)  TX bytes:2022 (1.9 KiB)

I started the domain like this:

  virt-install --connect lxc:/// --name alpine -r 512 \
    --filesystem /containers/alpine/,/ \
    -w network=default

When trying the same thing with a minimal Fedora domain, the above
failed because the Fedora filesystem I started with contained neither
`ip` or `ifconfig`...but worked fine once I installed the necessary
packages.

-- 
Lars Kellogg-Stedman <lars at redhat.com> | larsks @ {freenode,twitter,github}
Cloud Engineering / OpenStack          | http://blog.oddbit.com/

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