Add a volume
You can also use the VOLUME instruction in a Dockerfile to add one or more new volumes to any container created from that image.
docker run -d -P --name web -v /webapp training/webapp python app.py #add a volume /webapp for container web
docker inspect web
it will shows something like
"Mounts": [
{
"Name": "9773d6771225964ee795b675c3c05019fae21dfa7251264eb4a8e42fbc1e5232",
"Source": "/var/lib/docker/volumes/9773d6771225964ee795b675c3c05019fae21dfa7251264eb4a8e42fbc1e5232/_data",
"Destination": "/webapp",
"Driver": "local",
"Mode": "",
"RW": true,
"Propagation": ""
}
],
"Source" is the dir in the local host while "Destination" is the dir in the container.
Mount a host dir as a data volume
In addition to creating a volume using the -v flag you can also mount a directory from your Docker engine’s host into a container.
docker run -d -P --name web -v /src/webapp:/webapp:ro training/webapp python app.py
/src/webapp is the newly created dir in the host while /webapp is the dir in the container. "ro‘ means read only.
The host directory is, by its nature, host-dependent. For this reason, you can’t mount a host directory from Dockerfile because built images should be portable. A host directory wouldn’t be available on all potential hosts.
Mount a shared-storage volume as a data volume
In addition to mounting a host directory in your container, some Docker volume plugins allow you to provision and mount shared storage, such as iSCSI, NFS, or FC.