Changes

== Migration sequence ==

== Migration sequence ==

The steps below look like those in regular live migration, but include one of more pre-dump stages.

The steps below look like those in regular live migration, but include one or more pre-dump stages.

=== Pre-dump ===

=== Pre-dump ===

Take tasks you're about to migrate and pre-dump them into some place. Tasks will remain running after pre-dump, unlike regular dump.

Take tasks you are about to migrate and pre-dump them into some place. Tasks will remain running after pre-dump, unlike regular dump.

  [src]# criu pre-dump --tree <pid> --images-dir <path-to-existing-directory-A>

  [src]# criu pre-dump --tree <pid> --images-dir <path-to-existing-directory-A>

The directory with images can be on a shared storage, or you can use [[disk-less migration]] to avoid the '''Copy''' step.

The directory with images can be on a shared storage, or you can use [[disk-less migration]] to avoid the '''Copy''' step.

Now you can either proceed to next step and do regular dump, or perform the pre-dump step again. In the latter case pre-dump would generate another set of pre-dump images which will contain memory, that has changed from previous step. Doing several pre-dump stages (or iterations) may reduce the amount of data dumped on dump stage and thus -- smaller freeze time.

Now you can either proceed to next step and do regular dump, or perform the pre-dump step again. In the latter case pre-dump would generate another set of pre-dump images which will contain memory changed after previous pre-dump. Doing several pre-dump iterations may reduce the amount of data dumped on dump stage and thus lead to shorter freeze time.

=== Dump ===

=== Dump ===

  [src]# criu dump --tree <pid> --images-dir <path-to-existing-directory-B> --prev-images-dir <path-to-directory-A-relative-to-B> --leave-stopped

  [src]# criu dump --tree <pid> --images-dir <path-to-existing-directory-B> --prev-images-dir <path-to-directory-A-relative-to-B> --leave-stopped

Note, that

Note that:

# this dump would work faster, than it would if there were no the pre-dump stage, as this dump only takes the memory that has changed, since the pre-dump step.

# this dump would work faster than without pre-dump, as this dump only takes the memory that has changed since the last pre-dump;

# the <code>--prev-images-dir</code> should contain path to the directory with pre-dump images ''relative to the directory where the dump images will be put''

# the <code>--prev-images-dir</code> should contain path to the directory with pre-dump images ''relative to the directory where the dump images will be put''.

=== Copy ===

=== Copy ===

Copy images to destination node:

Copy images to the destination node:

  [src]# scp -r <path-to-images-dir> <dst>:/<path-to-images>

  [src]# scp -r <path-to-images-dir> <dst>:/<path-to-images>

=== Restore ===

=== Restore ===

Go to the destination node and restore the apps from images on it:

On the destination node restore the apps from images:

  [dst]# criu restore --tree <pid> --images-dir <path-to-images>

  [dst]# criu restore --tree <pid> --images-dir <path-to-images>

=== Kill ===

=== Kill ===

If everything went OK you can return on the source node and kill stopped tasks on it.

If everything went OK you can kill stopped tasks on the source node:

  [src]# FIXME put command here

  [src]# FIXME put command here

[[Category: HOWTO]]

[[Category: HOWTO]]