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8 commits

Author SHA1 Message Date
Alexander Larsson
c199ed228b devmapper: Move init layer to top rather than bottom
The init layer needs to be topmost to make sure certain files
are always there (for instance, the ubuntu:12.10 image wrongly
has /dev/shm being a symlink to /run/shm, and we need to override
that). However, previously the devmapper code implemented the
init layer by putting it in the base devmapper device, which meant
layers above it could override these files (so that ubuntu:12.10
broke).

So, instead we put the base layer in *each* images devmapper device.
This is "safe" because we still have the pristine layer data
in the layer directory. Also, it means we diff the container
against the image with the init layer applied, so it won't show
up in diffs/commits.
2013-09-26 15:09:32 +00:00
Alexander Larsson
c6e8813c97 deviceset: Cleanup device sets on test end
We unmount all mounts and deactivate all device mapper devices to
make sure we're left with no leftovers after the test.
2013-09-26 15:09:32 +00:00
Alexander Larsson
251a7ed437 DeviceSet: Add UnmountDevice()
Right now this does nothing but add a new layer, but it means
that all DeviceMounts are paired with DeviceUnmounts so that we
can track (and cleanup) active mounts.
2013-09-26 15:09:31 +00:00
Alexander Larsson
bc7fa7b957 Limit the amount of prints during normal runs
This removes some Debugf() calls and chages some direct prints to
Debugf(). This means we don't get a bunch of spew when running the
tests.
2013-09-26 15:09:31 +00:00
Alexander Larsson
8f343ea65a devmapper: Base the device-mapper names on the root dir name
This means the default is "docker-*", but for tests we get separate
prefixes for each test.
2013-09-26 15:08:55 +00:00
Alexander Larsson
2b1dc8a8a3 devmapper: Add simple tool to test the DeviceSet commands 2013-09-26 15:08:54 +00:00
Alexander Larsson
0b12702c0c devmapper: Add DeviceSet device-mapper helper
This is a module that uses the device-mapper create CoW snapshots
You instantiate a DeviceSetDM object on a specified root (/var/lib/docker),
and it will create a subdirectory there called "loopback". It will
contain two sparse files which are loopback mounted into
a thin-pool device-mapper device called "docker-pool".

We then create a base snapshot in the pool with an empty filesystem
which can be used as a base for docker snapshots. It also keeps track
of the mapping between docker image ids and the snapshots in the pool.

Typical use of is something like (without error checking):

devices = NewDeviceSetDM("/var/lib/docker")
devices.AddDevice(imageId, "") // "" is the base image id
devices.MountDevice(imageId, "/mnt/image")
 ... extract base image to /mnt/image
devices.AddDevice(containerId, imageId)
devices.MountDevice(containerId, "/mnt/container")
... start container at /mnt/container
2013-09-26 15:08:54 +00:00
Alexander Larsson
739af0a17f Add libdevmapper wrapper 2013-09-26 15:08:54 +00:00