Migrating from Linux (keeping partitions at install time)

[David Chanters]

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)

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).

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

Thanks in advance for any help.

David
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[Jerry McAllister-2]

On Sat, Nov 07, 2009 at 09:34:48PM +0000, David Chanters 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)

If you have enough other room to install FreeBSD on the disk and that
/dev/hda2 partition is not right in the middle of space you need for
installing FreeBSD.   eg, as long as it is in some ignorable place/space
on the disk.

>
> 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 don't know if ext2 vs ext3 matters.   It might.  I would be inclined to
want to make a backup of everthing on that partition and keep it somewhere
you can get back to after FreeBSD is installed.  Either tar or rsync it
all to somewhere.  Dump(8) is sensitive to OS, so it is one circumstance
in which I do not recommend dump/restore for this type of backup.

Now, providing that ext3 thing is not a problem,  you can probably leave
that filesystem/partition there if you have plenty of other space to install
FreeBSD and set things up.   Then you would probably want to copy everything
from that old /home to a new one in FreeBSD space.  You would just mount the
old one as something like /oldhome and copy the stuff from it to whereever
you have space in FreeBSD - maybe a new /home filesystem.

Not so sure I did anything for your most important question - if ext2 s ext3
is a problem, but I hope the rest is helpful.

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

Yes, absolutely - mount it and copy it to a FreeBSD filesystem if you
plan to use it any amount.

Good luck,

////jerry

>
> Thanks in advance for any help.
>
> David
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[Frank Shute-2]

On Sat, Nov 07, 2009 at 09:34:48PM +0000, David Chanters 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)

Yes. Your Linux partitions will be shown when you get to fdisk, IIRC.
Don't touch them and just create further slices for your FreeBSD
installation.

I assume you've got space on your disk to create further slices. If
not and your Debian installation takes up your whole disk, you'll have
to create space within Debian....or buy another disk.

>
> 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).

You can mount your ext3 partition as ext2 from within FreeBSD.

Have a look at ext2fs(5).

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

You can't convert it to UFS without losing your data AFAIK, so your
best bet is to mount it somewhere from within FreeBSD and just copy
your data over to your FreeBSD /home (/home is symlinked to
/usr/home).

>
> Thanks in advance for any help.
>
> David

Regards,

--

 Frank

 Contact info: http://www.shute.org.uk/misc/contact.html


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[Frank Shute-2]

On Sat, Nov 07, 2009 at 05:35:58PM -0500, Jerry McAllister wrote:
>
[snip]
>
> Not so sure I did anything for your most important question - if ext2 s ext3
> is a problem, but I hope the rest is helpful.
>

No, it's not a problem Jerry. ext3 is basically ext2 + journal, so you
can mount it at as ext2 from within FreeBSD (or Linux).

The journal sorts itself out when you boot Linux and it mounts the
filesystem as ext3.


Regards,

--

 Frank

 Contact info: http://www.shute.org.uk/misc/contact.html


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[Carl Johnson]

Frank Shute <frank@...> writes:

> On Sat, Nov 07, 2009 at 05:35:58PM -0500, Jerry McAllister wrote:
>>
> [snip]
>>
>> Not so sure I did anything for your most important question - if ext2 s ext3
>> is a problem, but I hope the rest is helpful.
>>
>
> No, it's not a problem Jerry. ext3 is basically ext2 + journal, so you
> can mount it at as ext2 from within FreeBSD (or Linux).
>
> The journal sorts itself out when you boot Linux and it mounts the
> filesystem as ext3.

I haven't been able to mount some ext3 filesystems.  When I
experimented, it appears that most new ext3 filesystems default to 256
byte inodes.  When I created a filesystem with 128 byte inodes then
FreeBSD could mount it just fine.  I didn't try ext2, but I think the
inode is independent of ext2 or ext3.  This is for FreeBSD
7.1-RELEASE, so maybe things have changed for 7.2 or 8.0.

--
Carl Johnson carlj@...


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[Ruben de Groot]

On Sat, Nov 07, 2009 at 10:18:21PM -0800, Carl Johnson typed:

> Frank Shute <frank@...> writes:
>
> > On Sat, Nov 07, 2009 at 05:35:58PM -0500, Jerry McAllister wrote:
> >>
> > [snip]
> >>
> >> Not so sure I did anything for your most important question - if ext2 s ext3
> >> is a problem, but I hope the rest is helpful.
> >>
> >
> > No, it's not a problem Jerry. ext3 is basically ext2 + journal, so you
> > can mount it at as ext2 from within FreeBSD (or Linux).
> >
> > The journal sorts itself out when you boot Linux and it mounts the
> > filesystem as ext3.
>
> I haven't been able to mount some ext3 filesystems.  When I
> experimented, it appears that most new ext3 filesystems default to 256
> byte inodes.  When I created a filesystem with 128 byte inodes then
> FreeBSD could mount it just fine.  I didn't try ext2, but I think the
> inode is independent of ext2 or ext3.  This is for FreeBSD
> 7.1-RELEASE, so maybe things have changed for 7.2 or 8.0.

This has been patched:

http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/124621

Ruben
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[Giorgos Keramidas]

On Sat, 7 Nov 2009 21:34:48 +0000, David Chanters <david.chanters@...> 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.

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[Carl Johnson]

Ruben de Groot <mail25@...> writes:

> On Sat, Nov 07, 2009 at 10:18:21PM -0800, Carl Johnson typed:
>> Frank Shute <frank@...> writes:
>>
>> > On Sat, Nov 07, 2009 at 05:35:58PM -0500, Jerry McAllister wrote:
>> >>
>> > [snip]
>> >>
>> >> Not so sure I did anything for your most important question - if ext2 s ext3
>> >> is a problem, but I hope the rest is helpful.
>> >>
>> >
>> > No, it's not a problem Jerry. ext3 is basically ext2 + journal, so you
>> > can mount it at as ext2 from within FreeBSD (or Linux).
>> >
>> > The journal sorts itself out when you boot Linux and it mounts the
>> > filesystem as ext3.
>>
>> I haven't been able to mount some ext3 filesystems.  When I
>> experimented, it appears that most new ext3 filesystems default to 256
>> byte inodes.  When I created a filesystem with 128 byte inodes then
>> FreeBSD could mount it just fine.  I didn't try ext2, but I think the
>> inode is independent of ext2 or ext3.  This is for FreeBSD
>> 7.1-RELEASE, so maybe things have changed for 7.2 or 8.0.
>
> This has been patched:
>
> http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/124621

Thanks for the information, but I notice that it was put into stable
*very* recently, so I hope it gets into 8.0-RELEASE.  I wasn't too
worried about it since the workaround was obvious once I identified
the problem.  I actually prefer to use Reiserfs, but it appears that
nobody is working on rw access for it.  Like the original poster, I am
a Debian user who is experimenting with it, but from VirtualBox for
now.  I will probably try setting up dual boot when 8.0 comes out.

--
Carl Johnson carlj@...


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