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Seeing as running things in containers doesn't appear to be supported in Ubuntu, my next best suggestion is to look at the IP address leases that dnsmasq is handing out. That's really simple:

$ cat /var/lib/misc/dnsmasq.leases

1363699477 00:16:3e:4a:ce:a4 10.0.3.83 containername *

There are only two parts there that are of any use, so we can format that up a lot nicer:

$ awk '{ print $4,$3 }' /var/lib/misc/dnsmasq.leases | column -t

containername  10.0.3.83

Technically speaking you should be able to use lxc-attach to connect and fire in a command (and process the output), like so:

sudo lxc-attach --name containername -- ifconfig

This requires the container to be running.

_{Note: I couldn't get this to work. I installed LXC and tried this but just saw a mush of namespace errors, missing files and other nonsense. But my only experience with LXC is the 10 minutes I've spent on this question. It might work. It might not. Good luck!}

This works on Ubuntu 14.04:

lxc-info -n $name -i

and if you want only the IP address (useful for scripts), (thanks @JulianHLam):

lxc-info -n $name -iH

Or query dnsmasq (which gives IPs to the containers)

dig @10.0.3.1 $container-name +short

The command below replaces lxc-attach example in previous post

sudo lxc-execute --name containername --rcfile /usr/share/doc/lxc/examples/lxc-macvlan.conf /sbin/ifconfig

It runs ifconfig inside the container and shows the output.

The --rcfile argument might not be required. Without it the command failed with 



lxc-execute: No such file or directory - failed to exec /usr/lib/lxc/lxc-init 



lxc-execute: invalid sequence number 1. expected 2

It sounds like something is not configured properly. As a workaround I've used the predefined configuration template provided by the LXC documentation to make it work without further investigation.

If you are running LXD, you may find this command useful for obtaining the IP address of a running container

lxc exec <container-name> -- ip addr show eth0 | grep "inetb" | awk '{print $2}' | cut -d/ -f1

Python version to do it :

#!/usr/bin/python

from pylxd import Client



client = Client(endpoint='https://10.185.96.208:8443', verify=False,    cert=('.config/lxc/client.crt', '.config/lxc/client.key'))



myCtr = client.containers.get('YOUR_CTR_NAME')

addresses = myCtr.state().network['eth0']['addresses']

for a in addresses:

   if(a['scope'] == 'global'):

      print "Found IP [%s]" %(a['address'])

      break

sudo lxc-ls --fancy -F ipv4 $my_container_name | tail -1

Let dnsmasq do it for you.

Configure your host machine's dnsmasq instance to query lxc's dnsmasq instance for the .lxc top-level domain.

In /etc/default/lxc-net, uncomment this line:

LXC_DOMAIN="lxc"

If your host's dnsmasq instance is launched by NetworkManager (as is the case with most current Ubuntu desktop installations) create a file called /etc/NetworkManager/dnsmasq.d/lxc.conf with this line inside:

server=/lxc/10.0.3.1

If your host's dnsmasq is launched by something other than NetworkManager, add that line to /etc/dnsmasq.d-available/lxc instead:

server=/lxc/10.0.3.1

Then restart things so they pick up the changes:

service lxc-net stop

service lxc-net start

service network-manager restart

You might have to restart your lxc containers or make them request new DHCP leases before they appear in DNS. (I don't remember whether it was necessary when I did this.) It's also worth mentioning that I saw a bug report about lxc-net not picking up dnsmasq changes when it was restarted, so you might want to reboot your host system just to be sure.

Then try it:

$ host mycontainer.lxc

mycontainer.lxc has address 10.0.3.21



$ ssh ubuntu@mycontainer.lxc

Welcome to Ubuntu 14.04.1 LTS (GNU/Linux 3.13.0-39-generic x86_64)

ubuntu@mycontainer:~$

Simple answer is

sudo lxc-ls -f | grep "container_name"

If you dont remember the container_name just type sudo lxc-ls -f.