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== Help 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.
<pre>
# 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)
</pre>
Below is an example to checkpoint and restore Docker container 4397:
<pre>
# docker_cr.sh -c 4397
dump successful
# docker_cr.sh -r 4397
restore successful
</pre>
Optionally, you can specify -v to see the commands that docker_cr.sh
executes. For example:
<pre>
# 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
</pre>
[[Category:HOWTO]]
[[Category:HOWTO]]