You should have built and installed a recent (>= 1.3.1) version of CRIU.
 Checkpointing and restoring a container
LXC upstream has begun to integrate checkpoint/restore support through the lxc-checkpoint tool. Although this functionality is not in any released version of LXC yet, you can check out the development version on Ubuntu by doing:
sudo add-apt-repository ppa:ubuntu-lxc/daily sudo apt-get update sudo apt-get install lxc
Next, create a container:
sudo lxc-create -t ubuntu -n u1 -- -r trusty -a amd64
And add the following lines (as above) to its config:
cat | sudo tee -a /var/lib/lxc/u1/config << EOF # hax for criu lxc.console = none lxc.tty = 0 lxc.cgroup.devices.deny = c 5:1 rwm EOF
Finally, start, and checkpoint the container:
sudo lxc-start -n u1 sleep 5s # let the container get to a more interesting state sudo lxc-checkpoint -s -D /tmp/checkpoint -n u1
At this point, the container's state is stored in /tmp/checkpoint, and the filesystem is in /var/lib/lxc/u1/rootfs. You can restore the container by doing:
sudo lxc-checkpoint -r -D /tmp/checkpoint -n u1
And then, get your container's IP and ssh in:
ssh ubuntu@$(sudo lxc-info -i -H -n u1)
Error (mount.c:805): fusectl isn't empty: 8388625.
Dumping of fuse filesystems is currently not supported. Empty the container's /sys/fs/fuse/connections and try again.
Error (mount.c:517): Mount 58 (master_id: 12 shared_id: 0) has unreachable sharing
criu doesn't yet support shared mountpoints as lxc does; make sure your rootfs is on a non-shared mount.