Crane can optionally make use of Unison to have faster bind-mounts between the host and Docker for Mac. Example configuration:
services:
hello:
image: alpine
rm: true
interactive: true
tty: true
volume:
- "foo:/bar"
accelerated-mounts:
hello:When Crane is asked to run the hello service, it automatically sets up an accelerated mount for foo:/bar. Behind the scenes, Crane starts a sync container (which is using Unison internally) connected to a plain Docker volume, which is then mounted to /bar in the hello container. From a user perspective however, everything looks as if the host directory foo is directly bind-mounted to /bar in the container.
Accelerated mounts can either be specified using a service name (then all configured bind-mounts of this service are accelerated), or by specifying a specific bind mount. The example above is equivalent to:
accelerated-mounts:
"foo:/bar":To reduce the amount of syncing that needs to be done, different containers or multiple instances of the same container definition share the same sync container and volume.
It is possible to customize each accelerated mount:
uid/gid: Defaults to 0/0. Set this to the user/group ID the consuming
container expects, e.g. 1000/1000.ignore: Defaults to
Name {.git} and allows to exclude files / folders from the sync. See Ignoring Paths for possible values.flags: Defaults to
["-auto", "-batch", "-ignore='Name {.git}'", "-confirmbigdel=false", "-contactquietly", "-prefer=newer"], but can be overriden using anything that
you can pass to unison, see its
manual.To debug what is happening when the sync is not behaving as expected, you can use:crane am logs -f hello. To remove the sync, use crane am reset hello.
uid/gid to non-root but notice that the synced folder itself is still owned by root, you need to create the (empty) folder with correct ownership in the Docker image. This is because accelerated mounts use volumes behind the scenes, and Docker will create non-existing mount points with root permissions.