add symlinking docker after setup

srvr-doc.md

@@ -55,9 +55,16 @@ two servers are relevant
 3. In /etc/systemd/system.conf: set CPU affinity
 4. restore /etc/gitlab-runner/config.toml
 5. restore /etc/sysctl/perf.conf
-6. Check if everything is running.
+6. symlink /var/lib/docker/ to /local/docker. This works with the following script:
+```
+systemctl stop docker
+mv /var/lib/docker /local/docker
+ln -s /local/docker /var/lib/docker
+systemctl start docker
+```
+7. Check if everything is running.
   + CPU Affinity: sanity-check in htop that only the cores that are configured in system.conf are running system processes
-7. Update the docker image at Docker Hub (the Debian version for the timing job needs to be the same as the host version, to have perf working), `ralfjung/opam-ci`. 
+8. Update the docker image at Docker Hub (the Debian version for the timing job needs to be the same as the host version, to have perf working), `ralfjung/opam-ci`. 
   Since the automatic pull from the Github repo doesn't work anymore, directly push to Docker Hub:
 ```
 git clone git@github.com:RalfJung/opam-ci.git opam-ci