Docker with Flannel overlay network

docker.service

[Unit]
Description=Docker Application Container Engine
Documentation=http://docs.docker.io
After=docker.socket
Requires=docker.socket
Requires=flannel.service
After=flannel.service

[Service]
Environment="TMPDIR=/var/tmp/"
EnvironmentFile=/run/flannel/subnet.env
EnvironmentFile=-/run/docker_opts.env
ExecStartPre=/bin/mount --make-rprivate /
# no-COW flag will propagate down the tree as directories are created by Docker - this is only important on first run
ExecStartPre=/usr/bin/chattr +C /var/lib/docker
LimitNOFILE=1048576
LimitNPROC=1048576
ExecStart=/bin/sh -c 'exec /usr/bin/docker --daemon --storage-driver=btrfs --host=fd:// --bip=${FLANNEL_SUBNET} --mtu=${FLANNEL_MTU} $DOCKER_OPTS'

flannel.service

[Unit]
Description=Flannel overlay network
Requires=etcd.service
After=etcd.service
Wants=network-online.target
After=network-online.target

[Service]
TimeoutStartSec=300
ExecStartPre=/bin/sh -c 'test -x /opt/bin/flanneld || wget -nv -O /opt/bin/flanneld deis-acp-aws-eu-west-1.s3-eu-west-1.amazonaws.com/bin/flanneld && chmod +x /opt/bin/flanneld'
ExecStartPre=/bin/sh -c 'i=0; while sleep 1; do i=$((i+1)); test $i -gt 20 && exit 1; etcdctl mk /coreos.com/network/config {\\"Network\\":\\"10.42.0.0/16\\"}; test $? -eq 0 -o $? -eq 4 && exit 0; done'
ExecStart=/opt/bin/flanneld
Restart=always

[Install]
RequiredBy=docker.service