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Line 1: − + − + − {{Note| This page was originally written a few months ago. Since then, interfacing with CRIU has been added to Docker's native exec driver (libcontainer) and pull requests to add checkpoint/restore functionality to Docker have been submitted. You can use one of the following Docker versions for your C/R experiments: + + − Docker 1.5 [https://github.com/SaiedKazemi/docker/wiki]+ − Docker 1.7 [https://github.com/boucher/docker/tree/cr-combined] − }} − There are two ways to checkpoint and restore a Docker container:+ + − + − done. − This is called external because it's happening external to the+ − Docker daemon. After checkpoint, the Docker daemon thinks that the − container has exited. After restore, the Docker daemon doesn't know that − the container is running again. Therefore, commands such as − <code>docker ps, stop, kill</code> and <code>logs</code> − will not work correctly. − {{Note| External C/R was done as proof-of-concept. Its use is discouraged and the helper script mentioned below will be deprecated in the near future.}}+ − + − <code>docker restore</code> commands. − Because the Docker daemon is involved in both checkpoint and restore,+ − its notion of the container state will be consistent and all commands such as − <code>docker ps, stop, kill </code> and <code>logs</code> will work. − This is obviously the preferred method of checkpointing and restoring Docker containers. − Native C/R is work in progress, say pre-alpha quality. You can+ − watch this short demo+ − '''[https://www.youtube.com/watch?v=HFt9v6yqsXo video]''' − to see how it works. Source files for Docker 1.5 C/R are at this − − The '''[https://github.com/SaiedKazemi/docker/wiki wiki]''' − page provides an overview of the project history. − Work in underway to integrate C/R into the new <code>libcontainer</code>. − For native C/R support, additional functionality was added to CRIU.+ − The most notable addition is the <code>--inherit-fd</code> command line option. − == External C/R ==+ − Starting with CRIU 1.3, it is possible to checkpoint and restore a+ − process tree running inside a Docker container. However, it's − important to note that Docker needs native support for checkpoint − and restore in order to maintain its parent-child relationship and − to correctly keep track of container states. In other words, while − CRIU can C/R a process tree, the restored tree will not become a − child of Docker and, from Docker's point of view, the container's − state will remain "Exited" (even after successful restore). − It's important to re-emphasize that by checkpointing and restoring+ − a Docker container, we mean C/R of a process tree running inside a − container, excluding the Docker daemon itself. As CRIU currently − does not support nested PID namespaces, the C/R process tree cannot − include the Docker daemon which runs in the global PID namespace. − == Command Line Options ==+ − In addition to the usual CRIU command line options used when+ − checkpointing and restoring a process tree, the following command − line options are needed for Docker containers. − === <code>--root</code> ===+ − This option has been used in the past only for restore operations+ − that wanted to change the root of the mount namespace. It was not − used for checkpoint operations. − However, because Docker by default uses the AUFS graph driver and+ − the AUFS module in the kernel reveals branch pathnames in − <code>/proc/''pid''/map_files</code>, option <code>--root</code> − is used to specify the root of the − mount namespace. Once the kernel AUFS module is fixed, it won't − be necessary to specify this option anymore. − + − This option is used to specify the path of the external bind mounts.+ − Docker sets up <code>/etc/{hostname,hosts,resolv.conf}</code> as targets with − source files outside the container's mount namespace. Older versions − of Docker also bind mount <code>/.dockerinit</code>. − For example, assuming the default Docker configuration, <code>/etc/hostname</code>+ − in the container's mount namespace is bind mounted from the source+ − at <code>/var/lib/docker/containers/''container_id''/hostname</code>.+ + + + + + + + − === <code>--manage-cgroups</code> === − When a process tree exits after a checkpoint operation, the cgroups+ − − is needed during restore to move the process tree into its cgroups, − re-creating them if necessary. − + − + − − − the global <code>/dev/null</code> and the container <code>/dev/null</code> as the same device. − == Restore Prework ==+ − As mentioned earlier, by default Docker uses AUFS to set up the+ − container's filesystem. When Docker notices that the process has − exited (due to CRIU dump), it dismantles the filesystem. We need − − + − Below is an example to show C/R operations for a shell script that+ − continuously appends a number to a file. You can use tail -f to − see the process in action. − As you will see below, after restore, the process's parent is PID+ − 1 (init), not Docker. Also, although the process has been successfully+ − restored, Docker still thinks that the container has exited. − To set up the container's AUFS filesystem before restore, its branch+ − information should be saved before checkpointing the container. − For convenience, however, AUFS branch information is saved in the − dump.log file. So we can examine dump.log to set up the filesystem − again. − For brevity, the 64-character long container ID is replaced by the+ − string <container_id> in the following lines.+ + + − <pre>+ − $ docker run -d busybox:latest /bin/sh -c 'i=0; while true; do echo $i >> /foo; i=$(expr $i + 1); sleep 3; done' − <container_id> − $ − $ docker ps − CONTAINER ID IMAGE COMMAND CREATED STATUS − 168aefb8881b busybox:latest "/bin/sh -c 'i=0; 6 seconds ago Up 4 seconds − $ − $ sudo criu dump -o dump.log -v4 -t 17810 \ − -D /tmp/img/<container_id> \ − --root /var/lib/docker/aufs/mnt/<container_id> \ − --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 \ − --manage-cgroups \ − --evasive-devices − $ − $ sudo grep successful /tmp/img/<container_id>/dump.log − (00.020103) Dumping finished successfully − $ − $ docker ps -a − CONTAINER ID IMAGE COMMAND CREATED STATUS − 168aefb8881b busybox:latest "/bin/sh -c 'i=0; 6 minutes ago Exited (-1) 4 minutes ago − $ − $ sudo mount -t aufs -o br=\ − /var/lib/docker/aufs/diff/<container_id>:\ − /var/lib/docker/aufs/diff/<container_id>-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/<container_id> − $ − $ sudo criu restore -o restore.log -v4 -d − -D /tmp/img/<container_id> \ − --root /var/lib/docker/aufs/mnt/<container_id> \ − --ext-mount-map /etc/resolv.conf:/var/lib/docker/containers/<container_id>/resolv.conf \ − --ext-mount-map /etc/hosts:/var/lib/docker/containers/<container_id>/hosts \ − --ext-mount-map /etc/hostname:/var/lib/docker/containers/<container_id>/hostname \ − --ext-mount-map /.dockerinit:/var/lib/docker/init/dockerinit-1.0.0 \ − --manage-cgroups \ − --evasive-devices − $ − $ sudo grep successful /tmp/img/<container_id>/restore.log − (00.424428) Restore finished successfully. Resuming tasks. − $ − $ ps -ef | grep /bin/sh − root 18580 1 0 12:38 ? 00:00:00 /bin/sh -c i=0; while true; do echo $i >> /foo; i=$(expr $i + 1); sleep 3; done − $ − $ docker ps -a − CONTAINER ID IMAGE COMMAND CREATED STATUS − 168aefb8881b busybox:latest "/bin/sh -c 'i=0; 7 minutes ago Exited (-1) 5 minutes ago − $ − </pre> − − == 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.+ − <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 <code>-v</code> to see the commands that <code>docker_cr.sh</code>+ − 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+ + + + + − + − − The OverlayFS filesystem was merged into the upstream Linux kernel 3.18 and is now Docker's preferred filesystem (instead of AUFS). For successful C/R, however, you need to apply the following kernel patch: − − OverlayFS patch [https://lkml.org/lkml/2015/3/20/372] − − − + − + + − +
→TTY: Update info about support for checkpointing of an interactive container
This HOWTO page describes how to checkpoint and restore a Docker container.
This article describes the status of CRIU integration with Docker, and how to use it.
== Introduction ==
== Docker Experimental ==
Naturally, Docker wants to manage the full lifecycle of processes running inside its containers, so CRIU should be run by Docker (rather than separately).
This feature is available in the ''experimental'' mode for Docker (since Docker 1.13, so every later version, like Docker 17.03, should work).
To enable experimental features (incl. CRIU), you need to do something like this:
echo "{\"experimental\": true}" >> /etc/docker/daemon.json
systemctl restart docker
'''External C/R''' using CRIU directly on the command line as it's typically
In addition to having a recent version of Docker, you need '''CRIU''' 2.0 or later installed on your system (see [[Installation]] for more info).
=== checkpoint ===
There's a top level <code>checkpoint</code> sub-command in Docker, which lets you create a new checkpoint, and list or delete an existing checkpoint. These checkpoints are stored and managed by Docker, unless you specify a custom storage path.
'''Native C/R''' using the newly added <code>docker checkpoint</code> and
Here's an example of creating a checkpoint, from a container that simply logs an integer in a loop.
First, we create container:
$ docker run -d --name looper --security-opt seccomp:unconfined busybox \
/bin/sh -c 'i=0; while true; do echo $i; i=$(expr $i + 1); sleep 1; done'
'''[https://github.com/SaiedKazemi/docker/tree/cr repo]'''.
You can verify the container is running by printings its logs:
$ docker logs looper
If you do this a few times you'll notice the integer increasing. Now, we checkpoint the container:
$ docker checkpoint create looper checkpoint1
You should see that the process is no longer running, and if you print the logs a few times no new logs will be printed.
=== restore ===
Unlike creating a checkpoint, restoring from a checkpoint is just a flag provided to the normal container '''start''' call. Here's an example:
$ docker start --checkpoint checkpoint1 looper
If we then print the logs, you should see they start from where we left off and continue to increase.
=== <code>--ext-mount-map</code> ===
==== Restoring into a '''new''' container ====
Beyond the straightforward case of checkpointing and restoring the same container, it's also possible to checkpoint one container, and then restore the checkpoint into a completely different container. This is done by providing a custom storage path with the <code>--checkpoint-dir</code> option. Here's a slightly revised example from before:
$ docker run -d --name looper2 --security-opt seccomp:unconfined busybox \
/bin/sh -c 'i=0; while true; do echo $i; i=$(expr $i + 1); sleep 1; done'
# wait a few seconds to give the container an opportunity to print a few lines, then
$ docker checkpoint create --checkpoint-dir=/tmp looper2 checkpoint2
$ docker create --name looper-clone --security-opt seccomp:unconfined busybox \
/bin/sh -c 'i=0; while true; do echo $i; i=$(expr $i + 1); sleep 1; done'
$ docker start --checkpoint-dir=/tmp --checkpoint=checkpoint2 looper-clone
You should be able to print the logs from <code>looper-clone</code> and see that they start from wherever the logs of <code>looper</code> end.
that Docker had created for the container are removed. This option
=== <code>--evasive-devices</code> ===
=== Passing additional options ===
Docker bind mounts <code>/dev/null</code> on <code>/dev/stdin</code> for detached containers
[[Configuration files]] can be used to set additional CRIU options when performing checkpoint/restore of Docker containers. These options should be added in the file <code>/etc/criu/runc.conf</code> (in order to '''overwrite''' the ones set by runc/Docker). Note that the options stored in <code>~/.criu/default.conf</code> or <code>/etc/criu/default.conf</code> will be '''overwritten''' by the ones set via [[RPC]] by Docker.
(i.e., <code>docker run -d ...</code>). Since earlier versions of Docker used
<code>/dev/null</code> in the global namespace, this option tells CRIU to treat
For example, in order to checkpoint and restore a container with established TCP connections CRIU requires the <code>--tcp-established</code> option to be set. However, this option is set to false by default and it is currently not possible to change this behaviour via the command-line interface of Docker. This feature can be enabled by adding <code>tcp-established</code> in the file <code>/etc/criu/runc.conf</code>. Note that for this functionality to work, the version of [[https://github.com/opencontainers/runc runc]] must be recent enough to have the commit [[https://github.com/opencontainers/runc/commit/e157963054e1be28bcd6612f15df1ea561c62571 e157963]] applied.
An alternative solution is to use [https://podman.io/ Podman] which has support to specify <code>--tcp-established</code> on the command-line.
to set up the filesystem again before attempting to restore.
== An Example ==
=== Synopsis ===
Checkpoint
# docker checkpoint create --help
Usage: docker checkpoint create [OPTIONS] CONTAINER CHECKPOINT
Create a checkpoint from a running container
Options:
--checkpoint-dir string Use a custom checkpoint storage directory
--help Print usage
--leave-running Leave the container running after checkpoint
Restore
# docker start --help
Usage: docker start [OPTIONS] CONTAINER [CONTAINER...]
Start one or more stopped containers
Options:
-a, --attach Attach STDOUT/STDERR and forward signals
--checkpoint string Restore from this checkpoint
--checkpoint-dir string Use a custom checkpoint storage directory
--detach-keys string Override the key sequence for detaching a container
--help Print usage
-i, --interactive Attach container's STDIN
== Compatibility Notes ==
The latest versions of the Docker integration require at least version 2.0 of CRIU in order to work correctly. Additionally, depending on the storage driver being used by Docker, and other factors, there may be other compatibility issues that will attempt to be listed here.
=== TTY ===
Checkpointing an interactive container is supported by CRIU, runc and containerd, but not yet enabled in Docker.
(See [[https://github.com/moby/moby/pull/38405 PR 38405]] for more information.)
=== Seccomp ===
You'll notice that all of the above examples disable Docker's default seccomp support. In order to use seccomp, you'll need a newer version of the Kernel. **Update Needed with Exact Version**
=== OverlayFS ===
There is a bug in OverlayFS that reports the wrong mnt_id in /proc/<pid>/fdinfo/<fd> and the wrong symlink target path for /proc/<pid>/<fd>. Fortunately, these bugs have been fixed in the kernel v4.2-rc2. The following small kernel patches fix the mount id and symlink target path issue:
* {{torvalds.git|155e35d4da}} by David Howells
* {{torvalds.git|df1a085af1}} by David Howells
* {{torvalds.git|f25801ee46}} by David Howells
* {{torvalds.git|4bacc9c923}} by David Howells
* {{torvalds.git|9391dd00d1}} by Al Viro
Assuming that you are running Ubuntu Vivid (Linux kernel 3.19), here is how you can patch your kernel:
<pre>
git clone git://kernel.ubuntu.com/ubuntu/ubuntu-vivid.git
cd ubuntu-vivid
git remote add torvalds git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
git remote update
git cherry-pick 155e35d4da
git cherry-pick df1a085af1
git cherry-pick f25801ee46
git cherry-pick 4bacc9c923
git cherry-pick 9391dd00d1
cp /boot/config-$(uname -r) .config
make olddefconfig
make -j 8 bzImage modules
sudo make install modules_install
sudo reboot
</pre>
</pre>
== OverlayFS ==
=== Async IO ===
== Async IO (AIO) ==
If you are using a kernel older than 3.19 and your container uses AIO, you need the following AIO kernel patches from 3.19:
If you are using a kernel older than 3.19 and your container uses AIO, you need the following AIO kernel patches from 3.19:
* {{torvalds.git|bd9b51e7}} by Al Viro
* {{torvalds.git|bd9b51e79c}} by Al Viro
* {{torvalds.git|e4a0d3e72}} by Pavel Emelyanov
* {{torvalds.git|e4a0d3e720}} by Pavel Emelyanov
== External checkpoint/restore ==
[[Category:HOWTO]]
Although it's not recommended, you can also learn more about using CRIU without integrating with Docker. See [[Docker External]] for more info.