OpenBSD -> FreeBSD migration

Andrew Wright andrewhw at
Sun Apr 20 20:10:30 UTC 2008

Hi All;

I want to migrate a system from OpenBSD 4.2 (ie; the current version)
to FreeBSD (7.0).  I have poked around on the archives a little
to determine how best to do this, and I want to make sure that
my understanding (summarized below) is indeed correct.  If I am
asking these questions on the wrong list (potentially likely for
the AMD specific questions) then please let me know:

Filesystem stuff:
   - it appears that FreeBSD and OpenBSD use the same partition
     table format.  Is this true?  If so, I can potentially avoid
     rebuilding an entire disk if I am right that ...
   - FreeBSD can mount and read OpenBSD's version of the 4.2 BSD
     filesystem implementation

   If both of these are true, I can simply install FreeBSD over
   top of the OpenBSD /, /var and /usr partitions, and then be
   able to mount the old /home.  Is this something people do?

   - even if the above isn't true, it appears that the format used
     by dump/restore is consistent.  I have tried dumping/restoring
     some small filesystems to test this, but if this is an unsupported
     way to go, I would like to know now.

     Also, before someone (quite rightly) says "back up your data",
     I will note that the reason that I would like to be able to read
     from /home is to avoid a lengthy restore -- all this data is
     backed up, but if there is no reason to re-label the drive and
     reformat the various user data partitions (on various drives) and
     then spend a day running restore, then I would like avoid such a
     waste of time.

     If this is even slightly likely to cause problems though, please
     let me know and I will start swapping media.

   - if I have somehow misled myself that restore(8) is consistent,
     please let me know -- re-installing the old OS just to back up
     to some other format would be a giant waste of time.

Processor stuff:
   - The machine of interest has an AMD64 processor.  I have seen
     several references to running Linux emulation on an AMD processor,
     but I would like to confirm that this is true while running the
     64-bit version of the OS.  In other words:
       - with a 64-bit installation (amd64) of FreeBSD 7.0, emulation
         of 32-bit Linux binaries (notably Matlab, but possibly other
         software as well) is possible, and indeed a reasonably
         well-known way of proceeding.

If I'm crazy, and/or misreading the docs, please let me know.


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