Volumes and mounts

Mount a directory, a volume or a tmpfs

var definition = new ContainerDefinition(ImageSource.FromRegistry("redis:8"));
definition.Mounts.AddBindMount("/host/data", "/data", readOnly: true);
definition.Mounts.AddVolume("existing-volume", "/var/lib/redis");
definition.Mounts.AddTmpfs("/scratch");

Method	Mounts
`AddBindMount(hostPath, containerPath, readOnly)`	A file or directory of the host. Use it to give test data or configuration files to the container.
`AddVolume(volumeName, containerPath, readOnly)`	A volume of the runtime, by name.
`AddVolume(volume, containerPath, readOnly)`	A TemporaryVolume, created before the container (see below).
`AddTmpfs(containerPath)`	A file system in memory, empty at every start. Use it for scratch space, or with a read-only root file system.

A tmpfs mount takes no more than half of the memory of the host by default. Pass a size, in bytes, and the permissions of its root to limit it:

definition.Mounts.AddTmpfs("/scratch", size: 64L * 1024 * 1024, mode: UnixFileMode.UserRead | UnixFileMode.UserWrite | UnixFileMode.UserExecute);

Apple's container does not take options for a tmpfs mount.

The BindMount, VolumeMount and TmpfsMount records describe the same mounts; pass one to Mounts.Add.

Create a volume for the test

A TemporaryVolume creates a volume and removes it when disposed, so a test can keep data across two containers without leaving anything behind:

await using var volume = new VolumeDefinition().CreateVolume();

var definition = new ContainerDefinition(ImageSource.FromRegistry("redis:8"));
definition.Mounts.AddVolume(volume, "/data"); // add `readOnly: true` for a read-only mount

await using var container = definition.CreateContainer();
await container.StartAsync(); // creates the volume if needed, then the container

StartAsync creates the volume when it does not exist yet, then the container, so the mount never resolves to an empty volume the runtime created on its own.
Declare the volume before the containers that mount it, so it is disposed last: a runtime refuses to remove a volume that a container still references.
Several containers can mount the same TemporaryVolume and start at the same time.

Volume settings

VolumeDefinition sets the name, the driver and its options, and the labels of the volume:

var volumeDefinition = new VolumeDefinition { Driver = "local" };
volumeDefinition.DriverOptions.Add("type", "tmpfs");
volumeDefinition.DriverOptions.Add("device", "tmpfs");
volumeDefinition.Labels.Add("com.example.suite", "integration");

await using var volume = volumeDefinition.CreateVolume();

Without a Name, the volume gets a random name.
The volume is only removed when the library created it. A Name that already exists is adopted and left behind.
A volume with a ReuseId is kept on dispose, so the next run reuses it. See Reusing a container.
CreateVolume copies the definition: the volume owns a read-only copy, as containers do.

Anonymous volumes

Some images declare volumes of their own (a VOLUME instruction in the Dockerfile). The runtime creates an anonymous volume for each one, and the library removes them with the container, except with wslc, which has no option for it.

Runtime differences

wslc has no volume commands: a TemporaryVolume throws a NotSupportedException there.
Apple's container has no volume driver, and its mount descriptors cannot contain a comma. As of version 1.1.0, it hangs on a container that mounts a volume a deleted container used, so keep a volume to a single container there.