OpenBSD -> FreeBSD migration

andrew clarke mail at
Sun Apr 20 21:02:20 UTC 2008

On Sun 2008-04-20 15:59:14 UTC-0400, Andrew Wright (andrewhw at wrote:

>   - 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

My understanding is that the second ISO image of FreeBSD (eg.
7.0-RELEASE-i386-disc2.iso) is a "Live CD".  That should enable you to
boot FreeBSD from CD and attempt to mount the file system (read-only
or read-write) that your OpenBSD installation lives on.

>   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?

I think prior to the FreeBSD install you would want to erase all files
in /, /var and /usr to remove any cruft that would be otherwise left
over from the previous OpenBSD installation.

Maybe I'm paranoid, but I would be wary of file system reliability
between two OSes, especially on a production system.  On the other
hand maybe there is someone reading this who is successfully dual
booting FreeBSD and OpenBSD and sharing /home that may want to comment
further.  Failing that, you could do some testing on a spare PC or in
a VM.

I can't comment on the dump/restore or Linux compatibility.

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