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Initial article
The <code>crtools</code> utility can be used to perform live migration of apps or containers. This page is a sort of HOWTO describing this.
In order to live-migrate an application or a container you should make sure, that files, that are/can be accessed by processes you're migrating are available on both nodes -- source and destination. This can be achieved by using either shared file-system such as NFS, GlusterFS or CEPH, or by using <code>rsync</code> to copy files from one box to another. Further in this article we assume, that the file-system is the same on both sides.
So, in order to live migrate tasks you should do these steps:
;step 1
: Take tasks you're about to migrate and dump them into some place, asking <code>crtools</code> to leave them in stopped state after dump:
<pre>
# crtools dump --tree <pid> --images-dir <path-to-existing-directory> --leave-stopped
</pre>
The directory you put images to can reside on the shared file-system if you're using one. In this case you can proceed to step 3.
;step 2
: Copy images to destination node
<pre>
# scp -r <path-to-images-dir> <dst-node>/<path-to-images>
</pre>
;step 3
: Go to the destination node and restore the apps from images on it
<pre>
# crtools restore --tree <pid> --images-dir <path-to-images>
</pre>
; step 4
: If everything went OK you can return on the source node and kill stopped tasks on it.
In order to live-migrate an application or a container you should make sure, that files, that are/can be accessed by processes you're migrating are available on both nodes -- source and destination. This can be achieved by using either shared file-system such as NFS, GlusterFS or CEPH, or by using <code>rsync</code> to copy files from one box to another. Further in this article we assume, that the file-system is the same on both sides.
So, in order to live migrate tasks you should do these steps:
;step 1
: Take tasks you're about to migrate and dump them into some place, asking <code>crtools</code> to leave them in stopped state after dump:
<pre>
# crtools dump --tree <pid> --images-dir <path-to-existing-directory> --leave-stopped
</pre>
The directory you put images to can reside on the shared file-system if you're using one. In this case you can proceed to step 3.
;step 2
: Copy images to destination node
<pre>
# scp -r <path-to-images-dir> <dst-node>/<path-to-images>
</pre>
;step 3
: Go to the destination node and restore the apps from images on it
<pre>
# crtools restore --tree <pid> --images-dir <path-to-images>
</pre>
; step 4
: If everything went OK you can return on the source node and kill stopped tasks on it.