How to move Docker containers between different hosts?

Question

I cannot find a way of moving docker running containers from one host to another.

Is there any way I can push my containers to repositories like we do for images ? Currently, I am not using data volumes to store the data associated with applications running inside containers. So some data resides inside containers, which I want to persist before redesigning the setup.

Gdynia

Have a look at flocker github.com/ClusterHQ/flocker – Jacklighter

Note that you may wish to use save/load instead of export/import, as save preserves metadata and history. – Clarindaclarine

Should this be a comment to @aholt's answer? – Stile

docker save is for saving images, not containers. docs.docker.com/engine/reference/commandline/save – Resumption

Answer 1

You cannot move a running docker container from one host to another.

You can commit the changes in your container to an image with docker commit, move the image onto a new host, and then start a new container with docker run. This will preserve any data that your application has created inside the container.

NB: It does not preserve data that is stored inside volumes; you need to move data volumes manually to new host.

Nephology

docker-checkpoint could let you move a "running" container between hosts, if they both support CRIU. – Rafael

@DaveJarvis if you want to make that extensive of an edit I would suggest simply posting a new answer. – Nephology

I moved Lau's helpful comment into a more visible location. I thought the idea of a wiki was that anyone could edit an answer to improve it? – Confine

This isn't a wiki, and when you make major changes to someone else's answer you're putting words into their mouth. Editing a question to make minor correction is just fine, but if you need to add substantial new information it's generally better to just post a new answer (and consider adding a comment on the accepted answer pointing at the additional information). – Nephology

So, "Here's an answer, with no steps on how to accomplish it, and a vague warning that there's something else you may need to do, also with no steps on how to do that." – Apul

@JohnSmith I'm glad this almost-10-year-old answer was moving enough to inspire a comment! – Nephology

Answer 2

Alternatively, if you do not wish to push to a repository:

1. Export the container to a tarball

   docker export <CONTAINER ID> > /home/export.tar
   

2. Move your tarball to new machine

3. Import it back

   cat /home/export.tar | docker import - some-name:latest
   

Fireplace

Also does not preserve data that is stored inside volumes. – Resumption

How is this supposed to work? After the import I get new image, and then what? Just do a new run command? – Zigzag

This is actually a really bad suggestion, especially for containers running database. I tried this suggestion and it didn't work. Could it maybe work with stopping container first? – Zigzag

This suggestion was only really meant for an alternative. It might work for your situation, it might not. For me, I was setting up database replication docker containers at the time, and for the export/import, did not care about preserving the data, as I was running backups of the database data regularly out to a different tarball. For that, this worked perfectly. – Fireplace

Answer 3

What eventually worked for me, after lot's of confusing manuals and confusing tutorials, since Docker is obviously at time of my writing at peak of inflated expectations, is:

1. Save the docker image into archive:
   docker save image_name > image_name.tar
2. copy on another machine
3. on that other docker machine, run docker load in a following way:
   cat image_name.tar | docker load

Export and import, as proposed in another answers does not export ports and variables, which might be required for your container to run. And you might end up with stuff like "No command specified" etc... When you try to load it on another machine.

So, difference between save and export is that save command saves whole image with history and metadata, while export command exports only files structure (without history or metadata).

Needless to say is that, if you already have those ports taken on the docker hyper-visor you are doing import, by some other docker container, you will end-up in conflict, and you will have to reconfigure exposed ports.

Note: In order to move data with docker, you might be having persistent storage somewhere, which should also be moved alongside with containers.

Update 10/2023
Another very good way to migrate docker containers You can actually follow this upgrade script, but modified for moving instead of upgrading. You will also need docker compose on target machine.

1. Use autocompose.py from https://github.com/Red5d/docker-autocompose/ you can use it as docker container also

    cd ~
    mkdir ~/dockercontainers
    sudo docker container list -a > ~/dockercontainers/containers.txt
    cat  ~/dockercontainers/containers.txt
    
    CIDS=$(docker container list -a | sed '1d' | awk '{print $1}')
    for c in $CIDS; do mkdir ~/dockercontainers/$c ; docker run --rm -v /var/run/docker.sock:/var/run/docker.sock ghcr.io/red5d/docker-autocompose $c > ~/dockercontainers/$c/docker-compose.yml ; done 

2. Inspect composer files and move volume folders with data on new machine

3. Export Images and tags as txt files Images: mkdir dockersave && docker images > dockersave/images.txt tags: cat dockersave/images.txt | sed '1d' | awk '{ print "docker tag "$3" "$1":"$2 }'>> tags.txt

4. Perform actual Images export (you can commit them before this step if required) IDS=$(docker images | sed '1d' | awk '{print $3}') for c in $IDS; do docker save -o dockersave/$c.tar $c; done

5. Copy everything from dockersave and dockercontainers to target machine.

6. Load images onto new docker: cd dockersave/ IDS=$(ls *.tar) for c in $IDS; do docker load -i $c; done

7. Restore containers CIDS=$(cat ~/dockercontainers/containers.txt | sed '1d' | awk '{print $1}'); for c in $CIDS; do cd ~/dockercontainers/$c ; docker-compose up -d --no-deps --build ; done

If everything is fine, you will get bunch of OK messages and docker ps will display all of your containers.

Underpay

Hugely helpful. The "No command specified" message was driving me crazy. – Mimesis

The "No command specified" message was driving me crazy too. I use docker commit <container-id> stackstorm-local:2.9, and docker pull stackstorm-local:2.9 from another host. – Lamellicorn

same here, you just saved my container and my time ! – Molton

It should be noted that before doing the docker save and docker load, one should commit the container to the image sudo docker commit <container_id> image_name – Jostle

No, no, no. All the save/load procedure above did was create an unusably broken container on the destination machine. It loads, starts, runs, all without any errors, and then, when you try to use it, it's like it's not even there, it just plain doesn't work at all, it's like it's not running. It works 100% as expected on the machine saved from, and not at all on the destination. – Apul

What did work, though, was zipping the /var/lib/docker folder into an archive, copying, expanding it on the destination machine. Boom, done, everything works. Why people give all sorts of nonworking hoops to jump through and never mention this simple working solution, I have no idea. – Apul

@JohnSmith I guess that your solution works if there are no containers on target host already running... – Beating

This never uses the created tags.txt, resulting in refetching of the images – Luddite

Answer 4

Use this script: https://github.com/ricardobranco777/docker-volumes.sh

This does preserve data in volumes.

Example usage:

# Stop the container   
docker stop $CONTAINER

# Create a new image   
docker commit $CONTAINER $CONTAINER

# Save image
docker save -o $CONTAINER.tar $CONTAINER

# Save the volumes (use ".tar.gz" if you want compression)
docker-volumes.sh $CONTAINER save $CONTAINER-volumes.tar

# Copy image and volumes to another host
scp $CONTAINER.tar $CONTAINER-volumes.tar $USER@$HOST:

# On the other host:
docker load -i $CONTAINER.tar
docker create --name $CONTAINER [<PREVIOUS CONTAINER OPTIONS>] $CONTAINER

# Load the volumes
docker-volumes.sh $CONTAINER load $CONTAINER-volumes.tar

# Start container
docker start $CONTAINER

Guanabara

Didn't work for me on AWS Linux (Centos). In the endi I took the low tech approach of using docker inspect to find the volume dir, then manually copying that over. – Enzymology

@Enzymology Maybe something related to SELinux? Do you have SELinux enabled? – Guanabara

Got this: tar: Removing leading `/' from member names – Arriola

@Arriola That's a typical tar message. Not an error and not an even a warning. – Guanabara

This worked very well, however I would recommend renaming the $CONTAINER to different names for the example. This is because the $CONTAINER name may not be the same as the actual CONTAINER image name. Also as a side note, You dont need to use docker start or docker create if using docker-compose. You can just use docker-compose up with the same config from the original system, then continue with the instructions. – Thanasi

Is this works on Raspberrypi os? – Penton

What is "<previous container options>"? Is there some way to find this out? I can't remember exactly how I created the container, it was years ago. – Apul

Answer 5

From Docker documentation:

docker export does not export the contents of volumes associated with the container. If a volume is mounted on top of an existing directory in the container, docker export will export the contents of the underlying directory, not the contents of the volume. Refer to Backup, restore, or migrate data volumes in the user guide for examples on exporting data in a volume.

Hugibert

cluster hq shutdown... and BTW to migrate container the container should run on ZFS / any supported storage lun – Hygienic

Answer 6

I tried many solutions for this, and this is the one that worked for me :

1.commit/save container to new image :

1. ++ commit the container:
   # docker stop
   # docker commit CONTAINER_NAME
   # docker save --output IMAGE_NAME.tar IMAGE_NAME:TAG
   
   

ps:"Our container CONTAINER_NAME has a mounted volume at '/var/home'" ( you have to inspect your container to specify its volume path : # docker inspect CONTAINER_NAME )

2. ++ save its volume : we will use an ubuntu image to do the thing.
   # mkdir backup
   # docker run --rm --volumes-from CONTAINER_NAME -v ${pwd}/backup:/backup ubuntu bash -c “cd /var/home && tar cvf /backup/volume_backup.tar .”
   
   

Now when you look at ${pwd}/backup , you will find our volume under tar format.
Until now, we have our conatainer's image 'IMAGE_NAME.tar' and its volume 'volume_backup.tar'.

Now you can , recreate the same old container on a new host.

Maggs

Answer 7

docker export | gzip > .tar.gz

#new host gunzip < /mnt/usb/.tar.gz | docker import -

docker run -i -p 80:80 /bin/bash

Greenaway

Answer 8

if you are using docker desktop you can use this extension

or you can see this link and describe How does it work behind the scenes? and do it by your self.

Spital