Running docker in a network namespace

docker_in_netns.txt

# After creating the network namespace e.g. vo_none_none
# See https://unix.stackexchange.com/questions/686155/how-can-i-use-a-bind-mount-in-a-network-namespace
# The trick is to bind mount sys, as otherwise ip netns exec will create a mount namespace without it
# Note that each invocation of ip netns exec has its own mount namespace!
$ (on host) sudo -E unshare -m sh -c 'mount --bind /sys /sys; exec ip netns exec vo_none_none sudo --user archie --preserve-env bash'
$ (in netns) sudo umount /sys
$ (in netns) sudo dockerd --host=unix:///var/run/docker-netns.sock --data-root=/var/lib/docker-netns --default-runtime=runc
$ (in netns) DOCKER_OPTS="--dns=YOURDNSHERE" DOCKER_HOST=unix:///var/run/docker-netns.sock sudo --user archie --preserve-env docker ... # your docker command here