[CRIU] Docker HOWTO

[Saied Kazemi]

Great!  Here is some additional text for the HOWTO page that introduces
docker_cr.sh and explains its usage.

--Saied


Helper Script

As seen in the above examples, the CRIU command line for checkpointing and
restoring a Docker container is pretty long.  For restore, there is also
an additional step to set up the root filesystem before invoking CRIU.

To automate the C/R process, there is a helper script in the contrib
subdirectory of CRIU sources, called docker_cr.sh.  In addition to
invoking CRIU, this helper script sets up the root filesystem for AUFS,
UnionFS, and VFS for restore.

With docker_cr.sh, all you have to provide is the container ID.
If you don't specify a container ID, docker_cr.sh will list all running
containers and prompt you to choose one.  Also, as shown in the help
output below, by setting the appropriate environment variable, it's
possible to tell docker_cr.sh which Docker and CRIU binaries to use,
where Docker's home directory is, and where CRIU should save and look
for its image files.

# docker_cr.sh --help
Usage:
docker_cr.sh -c|-r [-hv] [<container_id>]
-c, --checkpoint checkpoint container
-h, --help print help message
-r, --restore restore container
-v, --verbose enable verbose mode

Environment:
DOCKER_HOME (default /var/lib/docker)
CRIU_IMG_DIR (default /var/lib/docker/criu_img)
DOCKER_BINARY (default docker)
CRIU_BINARY (default criu)

Below is an example to checkpoint and restore Docker container 4397:

# docker_cr.sh -c 4397
dump successful
# docker_cr.sh -r 4397
restore successful

Optionally, you can specify -v to see the commands that docker_cr.sh
executes.  For example:

# docker_cr.sh -c -v 40d3
docker binary: docker
criu binary: criu
image directory:
/var/lib/docker/criu_img/40d363f564e00a2f893579fa012a200e475dcf8df47f2a22b7dd0860ffc3d7bf
container root directory:
/var/lib/docker/aufs/mnt/40d363f564e00a2f893579fa012a200e475dcf8df47f2a22b7dd0860ffc3d7bf

criu dump -v4 -D
/var/lib/docker/criu_img/40d363f564e00a2f893579fa012a200e475dcf8df47f2a22b7dd0860ffc3d7bf
-o dump.log --manage-cgroups --evasive-devices --ext-mount-map
/etc/resolv.conf:/etc/resolv.conf --ext-mount-map /etc/hosts:/etc/hosts
--ext-mount-map /etc/hostname:/etc/hostname --ext-mount-map
/.dockerinit:/.dockerinit -t 5991 --root
/var/lib/docker/aufs/mnt/40d363f564e00a2f893579fa012a200e475dcf8df47f2a22b7dd0860ffc3d7bf

dump successful
(00.020827) Dumping finished successfully

# docker_cr.sh -r -v 40d3
docker binary: docker
criu binary: criu
image directory:
/var/lib/docker/criu_img/40d363f564e00a2f893579fa012a200e475dcf8df47f2a22b7dd0860ffc3d7bf
container root directory:
/var/lib/docker/aufs/mnt/40d363f564e00a2f893579fa012a200e475dcf8df47f2a22b7dd0860ffc3d7bf

mount -t aufs -o
/var/lib/docker/aufs/diff/40d363f564e00a2f893579fa012a200e475dcf8df47f2a22b7dd0860ffc3d7bf
/var/lib/docker/aufs/diff/40d363f564e00a2f893579fa012a200e475dcf8df47f2a22b7dd0860ffc3d7bf-init
/var/lib/docker/aufs/diff/a9eb172552348a9a49180694790b33a1097f546456d041b6e82e4d7716ddb721
/var/lib/docker/aufs/diff/120e218dd395ec314e7b6249f39d2853911b3d6def6ea164ae05722649f34b16
/var/lib/docker/aufs/diff/42eed7f1bf2ac3f1610c5e616d2ab1ee9c7290234240388d6297bc0f32c34229
/var/lib/docker/aufs/diff/511136ea3c5a64f264b78b5433614aec563103b4d4702f3ba7d4d2698e22c158
none
/var/lib/docker/aufs/mnt/40d363f564e00a2f893579fa012a200e475dcf8df47f2a22b7dd0860ffc3d7bf

criu restore -v4 -D
/var/lib/docker/criu_img/40d363f564e00a2f893579fa012a200e475dcf8df47f2a22b7dd0860ffc3d7bf
-o restore.log --manage-cgroups --evasive-devices --ext-mount-map
/etc/resolv.conf:/var/lib/docker/containers/40d363f564e00a2f893579fa012a200e475dcf8df47f2a22b7dd0860ffc3d7bf/resolv.conf
--ext-mount-map
/etc/hosts:/var/lib/docker/containers/40d363f564e00a2f893579fa012a200e475dcf8df47f2a22b7dd0860ffc3d7bf/hosts
--ext-mount-map
/etc/hostname:/var/lib/docker/containers/40d363f564e00a2f893579fa012a200e475dcf8df47f2a22b7dd0860ffc3d7bf/hostname
--ext-mount-map /.dockerinit:/var/lib/docker/init/dockerinit-1.0.0 -d
--root
/var/lib/docker/aufs/mnt/40d363f564e00a2f893579fa012a200e475dcf8df47f2a22b7dd0860ffc3d7bf
--pidfile
/var/lib/docker/criu_img/40d363f564e00a2f893579fa012a200e475dcf8df47f2a22b7dd0860ffc3d7bf/restore.pid

restore successful
(00.408807) Restore finished successfully. Resuming tasks.

root      6206     1  1 10:49 ?        00:00:00 /bin/sh -c i=0; while true;
do echo $i >> /foo; i=$(expr $i + 1); sleep 3; done



On Tue, Sep 9, 2014 at 5:10 AM, Pavel Emelyanov <xemul at parallels.com> wrote:

> On 09/03/2014 11:28 PM, Filipe Brandenburger wrote:
> > Acked-by: Filipe Brandenburger <filbranden at google.com>
> >
> > On Wed, Sep 3, 2014 at 12:27 PM, Saied Kazemi <saied at google.com> wrote:
> >> As promised, here is a shell script to simplify checkpointing and
> restoring
> >> a Docker container.  The usage is pretty simple and obvious.  Try
> >> docker_cr.sh --help to get started.  I suggest adding this file to the
> >> scripts subdirectory of CRIU and installing it where criu is installed,
> but
> >> I have not modified the Makefile.
> >>
> >> I'd like to acknowledge Filipe's time for his review and feedback.
> >>
> >> Cheers!
>
> Sorry for the delay. The patch is applied with the scripts/ -> contrib/
> directory change. Huge thanks!
>
>
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