Hi,

I plan to "convert" (==reinstall) my system to be 64bit.
Since I have an already working and configure 32bit Gentoo-
system I would like to do the migration as follows:

Create another / partition somwhere on my harddisk
Install/Create a new 64bit Gentoo root there.
If everything works fine: Delete 32bit-/ and move (cp -a or something
like that) the 64bit-/ onto the now empty 32bit-/.

BUT:
Are there any -- especiall system-related -- binaries or such,
which get an hardcoded compiled in, so they would fail to work
after / is moved to another place than where it was created?

Best regards
mcc

meino.cramer@gmx.de writes:

> I plan to "convert" (==reinstall) my system to be 64bit.
> Since I have an already working and configure 32bit Gentoo-
> system I would like to do the migration as follows:
>
> Create another / partition somwhere on my harddisk
> Install/Create a new 64bit Gentoo root there.
> If everything works fine: Delete 32bit-/ and move (cp -a or something
> like that) the 64bit-/ onto the now empty 32bit-/.

I would mount -o bind / /mnt/binroot and cp -a or something /mnt/bindroot
to the 32bit-/, so you don't copy things as /proc and /dev as well.

> BUT:
> Are there any -- especiall system-related -- binaries or such,
> which get an hardcoded compiled in, so they would fail to work
> after / is moved to another place than where it was created?

No. The path would still be the same, whatever the underlying device is.

Wonko

Alex Schuster <wonko@wonkology.org> [10-09-11 12:08]:
> meino.cramer@gmx.de writes:
>
> > I plan to "convert" (==reinstall) my system to be 64bit.
> > Since I have an already working and configure 32bit Gentoo-
> > system I would like to do the migration as follows:
> >
> > Create another / partition somwhere on my harddisk
> > Install/Create a new 64bit Gentoo root there.
> > If everything works fine: Delete 32bit-/ and move (cp -a or something
> > like that) the 64bit-/ onto the now empty 32bit-/.
>
> I would mount -o bind / /mnt/binroot and cp -a or something /mnt/bindroot
> to the 32bit-/, so you don't copy things as /proc and /dev as well.
>
> > BUT:
> > Are there any -- especiall system-related -- binaries or such,
> > which get an hardcoded compiled in, so they would fail to work
> > after / is moved to another place than where it was created?
>
> No. The path would still be the same, whatever the underlying device is.
>
> Wonko
>

I think there is some misunderstanding:

Before migration to 64bit:

/dev/sda3 is mounted on / and contains the 32bit Gentoo

/dev/sda10 is mounted on /home/mcc/migration and will contain the
stuff of the 64bit Gentoo

After migration I will *not* mount /dev/sda10 on / but will clear all
stuff from /dev/sda3 and move the contents from /dev/sda10 to
/dev/sda3.

Is still valid what you said under this premissions, Wonko?

Thanks a lot for your help in advance!
Best regards
mcc

On Sat, 11 Sep 2010 11:08:49 +0200, Alex Schuster wrote:

> I would mount -o bind / /mnt/binroot and cp -a or
> something /mnt/bindroot to the 32bit-/, so you don't copy things
> as /proc and /dev as well.

Or use the -x option with cp, although I prefer to use rsync -ax for this
type of thing.


--
Neil Bothwick

WindowError:01B Illegal error. Do NOT get this error.

On Sat, Sep 11, 2010 at 5:19 AM, <meino.cramer@gmx.de> wrote:
<SNIP>
> I think there is some misunderstanding:
>
> Before migration to 64bit:
>
> /dev/sda3 is mounted on / and contains the 32bit Gentoo
>
> /dev/sda10 is mounted on /home/mcc/migration and will contain the
> stuff of the 64bit Gentoo
>
> After migration I will *not* mount /dev/sda10 on / but will clear all
> stuff from /dev/sda3 and move the contents from /dev/sda10 to
> /dev/sda3.
>
> Is still valid what you said under this premissions, Wonko?
>
> Thanks a lot for your help in advance!
> Best regards
> mcc

Why not mount /dev/sda10 as root and be done with it.? No need to move anything.

Do the 64-bit install as you are suggesting. Do NOT install grub.

Place the 64-bit kernel in the current /boot pointing at /dev/sda10.

Modify grub.conf to allow you to boot either /dev/sda3 (your 32-bit
install) or /dev/sda10. (your 64-bit install)

Boot both installs a few times and test that each is working. (They
will be) Use the 64-bit install for a few days and make sure it's
working. When it is don't boot 32-bit for a week or two, just leaving
it there on the drive because almost certainly you will have forgotten
to copy something over. (I always do...) Only when you are comfortable
that 64-bit is working correctly delete the 32-bit on /dev/sda3 if you
need the disk space.

Remember, leaving /home out of the picture a Gentoo install takes
maybe 10GB. It's not that large. Probably less if you shared the
portage distfiles directory between the two.

It doesn't hurt very much to have multiple installs on the same drive
in different partitions. It's what I did playing with a stable and a
testing install. I eventually deleted the testing install and just
went with stable and a few testing application packages. (I still
don't understand why any normal user wants a ~amd64 install but that's
just me!) ;-)

Hope this helps,
Mark

Mark Knecht <markknecht@gmail.com> [10-09-11 17:08]:
> On Sat, Sep 11, 2010 at 5:19 AM, <meino.cramer@gmx.de> wrote:
> <SNIP>
> > I think there is some misunderstanding:
> >
> > Before migration to 64bit:
> >
> > /dev/sda3 is mounted on / and contains the 32bit Gentoo
> >
> > /dev/sda10 is mounted on /home/mcc/migration and will contain the
> > stuff of the 64bit Gentoo
> >
> > After migration I will *not* mount /dev/sda10 on / but will clear all
> > stuff from /dev/sda3 and move the contents from /dev/sda10 to
> > /dev/sda3.
> >
> > Is still valid what you said under this premissions, Wonko?
> >
> > Thanks a lot for your help in advance!
> > Best regards
> > mcc
>
> Why not mount /dev/sda10 as root and be done with it.? No need to move anything.

...because data access at the outer partitions are faster than those
in the middle...

>
> Do the 64-bit install as you are suggesting. Do NOT install grub.
>
> Place the 64-bit kernel in the current /boot pointing at /dev/sda10.
>
> Modify grub.conf to allow you to boot either /dev/sda3 (your 32-bit
> install) or /dev/sda10. (your 64-bit install)
>
> Boot both installs a few times and test that each is working. (They
> will be) Use the 64-bit install for a few days and make sure it's
> working. When it is don't boot 32-bit for a week or two, just leaving
> it there on the drive because almost certainly you will have forgotten
> to copy something over. (I always do...) Only when you are comfortable
> that 64-bit is working correctly delete the 32-bit on /dev/sda3 if you
> need the disk space.

In the docs on gentoo-wiki (or? somewhere else?) I read that some
kind of data are not portable namely databases...

> Remember, leaving /home out of the picture a Gentoo install takes
> maybe 10GB. It's not that large. Probably less if you shared the
> portage distfiles directory between the two.
>
> It doesn't hurt very much to have multiple installs on the same drive
> in different partitions. It's what I did playing with a stable and a
> testing install. I eventually deleted the testing install and just
> went with stable and a few testing application packages. (I still
> don't understand why any normal user wants a ~amd64 install but that's
> just me!) ;-)

The normal user like me want 64bit application to access more than
2GB per task.
In my case: Rendering and simulation takes a LOT of memory
especially when it comes to huge counts of vertice or particle
interactions.
Therefore I plan to install 8GByte RAM.

>
> Hope this helps,
> Mark

Yes Mark, it helps! Thanks a lot!

Best regards
mcc

On Sat, Sep 11, 2010 at 8:23 AM, <meino.cramer@gmx.de> wrote:
<SNIP>
>>
>> Why not mount /dev/sda10 as root and be done with it.? No need to move anything.
>
> *...because data access at the outer partitions are faster than those
> *in the middle...
>

OK, assuming it's really measurable in real life, but I'll point out
that you don't necessarily have to 'copy' data from partition to
partition to achieve that. I've used gparted to first delete what you
are terming /dev/sda3, then enlarge /dev/sda10 toward the side of the
drive where you want it, then shrink sda10 when you get it there.
Takes a lot of time but works for a dummy like me, and no need to mess
with fstab, etc., because it just remains sda10.

Granted, that simple example assumes there's nothing in the middle. If
there is then I typically shrink and move it also.

Not an ideal solution, but it works.

But the point remains that you can probably exist with both installs
on the drive for some _long_ period of time before you ever get around
to these steps for the sake of performance. Certainly don't get rid of
the working 32-bit install before you are _completely_ sure the 64-bit
is working.

- Mark

Mark Knecht <markknecht@gmail.com> [10-09-11 20:40]:
> On Sat, Sep 11, 2010 at 8:23 AM, <meino.cramer@gmx.de> wrote:
> <SNIP>
> >>
> >> Why not mount /dev/sda10 as root and be done with it.? No need to move anything.
> >
> > *...because data access at the outer partitions are faster than those
> > *in the middle...
> >
>
> OK, assuming it's really measurable in real life, but I'll point out
> that you don't necessarily have to 'copy' data from partition to
> partition to achieve that. I've used gparted to first delete what you
> are terming /dev/sda3, then enlarge /dev/sda10 toward the side of the
> drive where you want it, then shrink sda10 when you get it there.
> Takes a lot of time but works for a dummy like me, and no need to mess
> with fstab, etc., because it just remains sda10.
>
> Granted, that simple example assumes there's nothing in the middle. If
> there is then I typically shrink and move it also.
>
> Not an ideal solution, but it works.
>
> But the point remains that you can probably exist with both installs
> on the drive for some _long_ period of time before you ever get around
> to these steps for the sake of performance. Certainly don't get rid of
> the working 32-bit install before you are _completely_ sure the 64-bit
> is working.
>
> - Mark
>

Hi Mark,

sorry, but with gparted & Co, I made some experiences which let me
leave those tools alone. Maybe the problem sits right in front of my
monitor, but...

In my case, there is "something in the middle", thats why it is
/dev/sda3 and /dev/sd10 and not /dev/sda3 and /dev/sd4...
So things getting even more complex and especially complexer
than "cp" and friends...

Is there any "automagical check" whic does some basic checking, to
find the biggest bugs in a fresh 64bit-installation?
(Beside those, which are identical on 32bit and 64bit -- like emerge
and such...) ?

Best regards,
mcc

meino.cramer@gmx.de writes:

> I think there is some misunderstanding:
>
> Before migration to 64bit:
>
> /dev/sda3 is mounted on / and contains the 32bit Gentoo
>
> /dev/sda10 is mounted on /home/mcc/migration and will contain the
> stuff of the 64bit Gentoo
>
> After migration I will *not* mount /dev/sda10 on / but will clear all
> stuff from /dev/sda3 and move the contents from /dev/sda10 to
> /dev/sda3.
>
> Is still valid what you said under this premissions, Wonko?

That's how I understood it, although I assumed the temproary 64bit install
would be on a 2nd drive, thus you would copy it back once it seems to
work. No, I see no problem with this.

About performance: I'm not sure it will be even noticeable. Yes, most
drives (but not all) are organized so the first partitions go to the
outside, which is faster. With LVM, I used to create two volume groups on
my drive, a group for swap and the system, and another one for data. But
then I thought it's not worth the effort, and I lose some of the LVM
benefits. Well, with everything encrypted I don't get full performance
anyway, so my case might be a little different.

But the performance increase is only true when reading lots of data. I'm
not sure how big the role of this is in real life. Access time is not
influenced, it will on average take half a turn of the drive till the
heads can access the data, and to me it looks like typical stuff a linux
system does is reading many not so large files, cluttered around in the
file system. But that's my guess only. And I understand that you like to
optimize stuff - I like to do this too. But sometimes I think that the
potential benefit might not be so large, compared to the time I spend
moving data around to the ideal place, or the time I would need to spend
thinking about how to tune things. Or the time you need to fix a problem
that you know was working in the old system, but this is gone now and you
cannot have a quick look at it, or just boot into it. You lose the
opportunity to start your old system in order to compare the times of your
big renderings. And maybe at one point you need to create some true 32bit
applications? Happened to me. So I just chroot into my old system and
build there.

Oh, and you mentioned databases. Yes, mysql stores itsa data in machine-
depenent form. You will need to dump the data and re-import it in the new
system. You will be happy to still have the 32bit system in such a case

Wonko

Alex Schuster <wonko@wonkology.org> [10-09-12 04:13]:
> meino.cramer@gmx.de writes:
>
> > I think there is some misunderstanding:
> >
> > Before migration to 64bit:
> >
> > /dev/sda3 is mounted on / and contains the 32bit Gentoo
> >
> > /dev/sda10 is mounted on /home/mcc/migration and will contain the
> > stuff of the 64bit Gentoo
> >
> > After migration I will *not* mount /dev/sda10 on / but will clear all
> > stuff from /dev/sda3 and move the contents from /dev/sda10 to
> > /dev/sda3.
> >
> > Is still valid what you said under this premissions, Wonko?
>
> That's how I understood it, although I assumed the temproary 64bit install
> would be on a 2nd drive, thus you would copy it back once it seems to
> work. No, I see no problem with this.
>
> About performance: I'm not sure it will be even noticeable. Yes, most
> drives (but not all) are organized so the first partitions go to the
> outside, which is faster. With LVM, I used to create two volume groups on
> my drive, a group for swap and the system, and another one for data. But
> then I thought it's not worth the effort, and I lose some of the LVM
> benefits. Well, with everything encrypted I don't get full performance
> anyway, so my case might be a little different.
>
> But the performance increase is only true when reading lots of data. I'm
> not sure how big the role of this is in real life. Access time is not
> influenced, it will on average take half a turn of the drive till the
> heads can access the data, and to me it looks like typical stuff a linux
> system does is reading many not so large files, cluttered around in the
> file system. But that's my guess only. And I understand that you like to
> optimize stuff - I like to do this too. But sometimes I think that the
> potential benefit might not be so large, compared to the time I spend
> moving data around to the ideal place, or the time I would need to spend
> thinking about how to tune things. Or the time you need to fix a problem
> that you know was working in the old system, but this is gone now and you
> cannot have a quick look at it, or just boot into it. You lose the
> opportunity to start your old system in order to compare the times of your
> big renderings. And maybe at one point you need to create some true 32bit
> applications? Happened to me. So I just chroot into my old system and
> build there.
>
> Oh, and you mentioned databases. Yes, mysql stores itsa data in machine-
> depenent form. You will need to dump the data and re-import it in the new
> system. You will be happy to still have the 32bit system in such a case
>
> Wonko
>

I also cannot evaluate the real impact the position of the /-partition
on the harddisk has on system performance. I read about it years ago
and since than I always put the partitions always in the sequence of
"boot","swap","root","home" onto the harddisks. May be its only a
tradition nowadays...

Do you know of any other kind of data beside databses, which may be
machinedependant or cause trouble while migrating to 64bit?

Best regards,
mcc