Changes

66 bytes removed ,  18:26, 14 May 2013
minor typos, fixes, clarifications
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== Migration sequence ==
 
== Migration sequence ==
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The steps below look like those in regular live migration, but include one of more pre-dump stages.
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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.
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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>
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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.
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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.
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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 ===
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  [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
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Note, that
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Note that:
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# 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.
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# 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''
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# 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:
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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:
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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.
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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]]