Selecting a Storage Driver in Docker

This lab was performed on a CentOS 7 server running Docker CE
Get the current storage driver:
```
docker info
```
Set the storage driver explicitly by providing a flag to the Docker daemon:
```
sudo vi /usr/lib/systemd/system/docker.service
```
Edit the ExecStart line, adding the --storage-driver devicemapper flag:
```
ExecStart=/usr/bin/dockerd --storage-driver devicemapper ...
```
After any edits to the unit file, reload Systemd and restart Docker:
```
sudo systemctl daemon-reload
sudo systemctl restart docker
```
We can also set the storage driver explicitly using the daemon configuration file. This is the method that Docker recommends. Note that we cannot do this and pass the --storage-driver flag to the daemon at the same time:
```
sudo vi /etc/docker/daemon.json
```
Set the storage driver in the daemon configuration file:
```
{
  "storage-driver": "devicemapper"
}
```
Restart Docker after editing the file. It is also a good idea to make sure Docker is running properly after changing the configuration file:
```
sudo systemctl restart docker
sudo systemctl status docker
```