Ubuntu – Copy lxd containers between hosts

containerslxcUbuntu

I've installed lxd on two ubuntu hosts that can only communicate via an intermediate server (on which I don't have su privileges). I've created a container on my localhost and now wish to load the container on the remote server.

I consulted the basic.sh test script in the lxc/lxd repo to confirm that I'm using the correct approach (I discovered along the way that I was misunderstanding images vs containers).

I've created a container test on my localhost, installed all the necessary goodies within it, stopped it, published it, and executed the following commands:

lxc image export test

This gives me a tarball 42cf01c53cb9e…83e3c48.tar.gz (shortened here), as described in the documentation (I'm running lxc and lxd versions 2.0.0.beta3). Attempting to import that image on the same host via

lxc image import 42cf01c53cb9e...83e3c48.tar.gz --alias testimage

yields the error:

exit status 2 (tar: metadata.yaml: Not found in archive)

The basic.sh script leads me to believe that I was following the correct route though (except for the tar.gz vs tar.xz descrepancY). I'm able to export standard images and obtain an .xz file (when I obtain them using lxd-images). For example, 

lxd-images import ubuntu --alias ubuntu
lxc image export ubuntu

produces a meta-ubuntu…tar.xz and ubuntu…tar.xz file, which can be imported (on a different server) with 

lxc image import meta...tar.xz rootfs ubuntu...tar.xz --alias imported_ubuntu

How do I copy containers between hosts?

Thanks!

Edit: I've investigated further and have published my test container, which creates an image of it. Then I get the .gz file though (without the meta-data) when I export it. If I hijack metadata from the original image, then I can't get the container started although import no longer crashes on me — I obviously don't know what I'm doing. Pulling the image over to a second host using lxd's remote: approach (after adding the host using the lxd config) does not result in it appearing in lxc images list.

Best Answer

The later release (non-beta) of lxd (v2.0) seems to have resolved my issue. The steps, which may be found in the excellent documentation here, are:

  1. Publish an image (without stopping the container) on host A;

    $ lxc publish --force container_name --alias image_name
Container published with fingerprint: d2fd708361...a125d0d5885

  2. Export the image to a file;

    $ lxc image export image_name 
Output is in dd2fd708361...a125d0d5885.tar.gz

  3. Copy the file to host B, and import;

    $ lxc image import dd2fd708361...a125d0d5885.tar.gz --alias image_name
Transferring image: 100%

  4. Launch the container (from the image) on host B;

    $ lxc launch image_name container_name
Creating container_name
Starting container_name

In some instances the publish command may lead to a split xz tar-ball --- but both formats are supported. Simply import the meta-data and rootfs components with 

    lxc image import <metadata tarball> <rootfs tarball> --alias image_name
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