Migrating from Linux (keeping partitions at install time)

[Giorgos Keramidas]

On Sat, 7 Nov 2009 21:34:48 +0000, David Chanters <david.chanters at googlemail.com> wrote:
> Hi all,
>
> I am considering switching from Debian Linux to FreeBSD.  I am wondering
> if at install time, sysinstall is able to allow me to keep "/home" from
> my Debian installation.  "/home" on Debian is currently a separate
> partition in its own right, mounted as RXT3.  I only have the one hard
> disk in my machine.
>
> So, questions:
>
> 1. Can the installer be told to not touch "/home" at install time (I
> appreciate I would have to ensure I mapped the current /dev/hda2
> terminology to slices in BSD parlance)

Hi David,

Yes, you can use sysinstall to _carefully_ partition and label only parts
of an existing disk.  It is certainly possible, but it is also slightly
risky.  One mistake and you can wipe tons of useful data.

My own advice would be to *wait* until you have at least some way to backup
your existing data.  First make sure that you have a working and reliable
copy of your existing data (meaning "you can read *all* of it from the
backup medium and verify that it matches the existing files").  Then you
can start experimenting with partitioning tools.

We will be glad to have you as a FreeBSD user, and you asked at the right
place.  But losing data is always a bad thing, so it's ok if you keep using
Debian for a while, until you have a reliable backup of everything.

> 2. Does the fact that this is an EXT3 partition matter?  (I have read
> FreeBSD supports ext2, and ext3 is just ext2 with a journal, so it can be
> mounted as ext2 if needed).

I've seen ext3 partitions that are not mountable by our ext2fs driver.  So
your mileage may vary a lot here, depending on the exact on-disk format of
your partition.  You should probably keep this in mind when you prepare
your backup mediums too.  If at all possible, try to use a filesystem for
the backup storage that is readable by both Linux *and* FreeBSD.

VFAT is a possibility, but its file size limitations and partition size
limitations are often annoying.

Network-accessible storage is better.

If nothing else works, you can always dump a "raw" tarball on a disk:

    linux# tar cf - / | dd bs=4m of=/dev/sda3

Then you can simply untar the "raw device" from FreeBSD.

> 3. Is it possible/beneficial to convert this to UFS once FreeBSD is
> installed?

There are a few benefits indeed.  The native filesystems of FreeBSD are
these days UFS and ZFS.  They are actively maintained, so you get the
benefit of bugfixes and extensive testing from everyone else who uses the
same filesystems.