[Nix-dev] Different behavior of cryopid on two "identical" machines

[Marco Maggesi]

Hi,

I have two (almost) identical machines but cryopid works in one and
fails in the other.

I would like to understand way.

(Cryopid is a checkpointing software, see
http://sharesource.org/project/cryopid
Cryopid is a fragile software an it is highly dependent on the system
e.g. on the kernel version.)

Both machines are virtualized with virtualbox, run the same kernel
versions (2.6.32), have (almost) identical configurations and use
the same svn revision of nixos/nixpkgs.

So, which are the possible explanations for this phenomenon?

I'm trying to compile a list of hypothesis:

1. disk corruption or other similar failures
2. the two machines run on different hosts (OSX and Linux) and
    different versions of virtualbox.
3. the few differences (essentially the extraPackages) in the
    configuration are significant.
4. the system software of the two machines is not identical since they
    are built following different upgrade paths.

I think that 1,2,3 are possible but very unlikely.

So I'm investigating 4.  Looking at the nix store I noticed that,
although rarely, some packages have different hashes.  For instance
the two machines have the same version of linux headers but with
different hashes.

I assume that this happens because the installed software is upgraded
only after a version bump.  Is that true?

In that case, how can I force the upgrade?

Thanks,
Marco