Some quick notes on how to get up and running with Docker.
Installation
On Fedora this turned out to be pretty easy, simply:
dnf install docker
For other systems see the Docker installation manual.
Start docker demon
systemctl status -l docker ● docker.service - Docker Application Container Engine Loaded: loaded (/usr/lib/systemd/system/docker.service; disabled; vendor preset: disabled) Active: active (running) since Sat 2015-12-12 22:40:41 GMT; 3min 35s ago Docs: http://docs.docker.com Main PID: 5818 (docker) CGroup: /system.slice/docker.service └─5818 /usr/bin/docker daemon --selinux-enabled Dec 12 22:40:01 asterix docker[5818]: time="2015-12-12T22:40:01.803909914Z" level=error msg="WARNING: No --storage-opt dm.thinpooldev specified, using loopback; this configuration is strongly discouraged for production use" Dec 12 22:40:40 asterix docker[5818]: time="2015-12-12T22:40:39.995085846Z" level=warning msg="Docker could not enable SELinux on the host system" Dec 12 22:40:40 asterix docker[5818]: time="2015-12-12T22:40:40.059743984Z" level=info msg="Option DefaultDriver: bridge" Dec 12 22:40:40 asterix docker[5818]: time="2015-12-12T22:40:40.059788786Z" level=info msg="Option DefaultNetwork: bridge" Dec 12 22:40:40 asterix docker[5818]: time="2015-12-12T22:40:40.388329409Z" level=info msg="Firewalld running: true" Dec 12 22:40:41 asterix docker[5818]: time="2015-12-12T22:40:41.278276562Z" level=info msg="Loading containers: start." Dec 12 22:40:41 asterix docker[5818]: time="2015-12-12T22:40:41.278585203Z" level=info msg="Loading containers: done." Dec 12 22:40:41 asterix docker[5818]: time="2015-12-12T22:40:41.278606222Z" level=info msg="Daemon has completed initialization" Dec 12 22:40:41 asterix docker[5818]: time="2015-12-12T22:40:41.278627443Z" level=info msg="Docker daemon" commit="cb216be/1.8.2" execdriver=native-0.2 graphdriver=devicemapper version=1.8.2-fc22 Dec 12 22:40:41 asterix systemd[1]: Started Docker Application Container Engine.
An interesting warning about no –storage-opt db.thinpooldev specified. This is related to Docker’s storage driver, which the docs explain in good detail.
Run Hello World
First, some info about the docker installation
docker info
It’s better to follow along the official and pretty good step by step documentation on basic docker usage, but the basics are below:
Run a single command
[root@asterix ~]# docker run ubuntu:14.04 /bin/echo 'Hello world' Hello world
Interactive shell
[root@asterix ~]# docker run -t -i ubuntu:14.04 /bin/bash root@8aed75e824e2:/# hostname 8aed75e824e2 root@8aed75e824e2:/# exit exit [root@asterix ~]#
Restart a container that was previously running
docker ps -a docker restart $CONTAINER_ID docker exec -it $CONTAINER_ID /bin/bash
Copy file from container to host
docker cp $CONTAINER_ID:$CONTAINER_PATH $HOST_PATH
Under the covers
Basic information about the newly created image:
[root@asterix ~]# docker images REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE docker.io/ubuntu 14.04 d55e68e6cc9c 4 days ago 187.9 MB
Local docker containers are stored in /var/lib/docker
[root@asterix ~]# ls -l /var/lib/docker/ total 36 drwx------ 5 root root 4096 Dec 12 23:09 containers drwx------ 5 root root 4096 Dec 12 22:50 devicemapper drwx------ 7 root root 4096 Dec 12 22:50 graph -rw-r--r-- 1 root root 5120 Dec 12 23:09 linkgraph.db -rw------- 1 root root 114 Dec 12 22:50 repositories-devicemapper drwx------ 2 root root 4096 Dec 12 22:50 tmp drwx------ 2 root root 4096 Dec 12 22:49 trust drwx------ 2 root root 4096 Dec 12 22:40 volumes
And we can see what looks like a ext4 filesystem:
[root@asterix ~]# file /var/lib/docker/devicemapper/devicemapper/data /var/lib/docker/devicemapper/devicemapper/data: Linux rev 1.0 ext4 filesystem data, UUID=6d11e0b5-f063-4a4f-99f4-36253b12b297 (extents) (large files) (huge files)
