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reworked
[[Category: Empty articles]]
Sometimes CRIU is unable to checkpoint or restore a process for various reasons. This article describes a way to check whether CRIU works or not for a given case.
== Rationale ==
It might be the case that a process can not be dumped at all (see [[what cannot be checkpointed]]), or that there are some problems which can be fixed. One way to check if checkpoint/restore will work is to run <code>criu dump</code> with {{Opt|--leave-running}} on the source system, copy the dump over, then run <code>criu restore</code> on the destination.
The problems with the above approach are:
* If restore succeeds, one will have two sets of same processes running on two machines, which may have disastrous effects;
* A lot of memory is dumped to disk and transferred to the destination system, which is not necessary for a test run.
To solve these, an easier and faster way to test if dump/restore will work, <code>--check-only</code> option was introduced.
== Usage ==
Source system:
# criu dump --check-only -D /tmp/cp -t <PID>
Only checking if requested operation will succeed
...
# rsync -a /tmp/cp dest-system:/tmp
Destination system:
# criu restore -D /tmp/cp
Checking mode enabled
...
Upon restore, CRIU will see that the checkpoint is a check-only one, and will do restore in a check-only mode automatically, so there is no need to supply this option explicitly.
=== Restore-only ===
One can use the ''--check-only'' switch on a full checkpoint, to see if the restore will succeed, at the same time making sure the process will not start running:
Destination system:
# criu restore --check-only -D /tmp/cp
Only checking if requested operation will succeed
Checking mode enabled
...
Currently only the existing checks (e.g., check binary size) are run in check-only mode,
but additional checks could be added, for example:
* checksums of binaries
* checksums of used libraries
* available memory
[[Category: Using]]
[[Category: Using]]