[gentoo-user] Moving the system from one disk to another

[gentoo-user] Moving the system from one disk to another

[meino.cramer]

Hi,

I have to move my whole system from one disk to another
bigger one.

I think of doing as follows:
Boot a system via CD/DVD (knoppix for example).
Mount small disk read-only 
Mount bigger disk read-write

cd into mountpoint of the first one
cp -a . ../<mountpoint_of_bigger_disk>

Seems to me slow but correct? Or?

(I have to set the bootable flag of the correct partion
additionally...)

I dont want to have a booting system afterwards, which "runs" for --
say -- three month and suddenly hit a obscure bug due to my
copy-commands, which only did it to 99.87% correct... ;)

I would like to preserve as much as possible of the file/directoy
times ,,,

Or does a mystical command with s-tar a better job faster? 

Thank you very much in adance for any help!

Best regards,
mcc

-- 
Please don't send me any Word- or Powerpoint-Attachments
unless it's absolutely neccessary. - Send simply Text.
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In a world without fences and walls nobody needs gates and windows.

Re: [gentoo-user] Moving the system from one disk to another

[covici]

meino.cramer@gmx.de wrote:

> 
> Hi,
> 
> I have to move my whole system from one disk to another
> bigger one.
> 
> I think of doing as follows:
> Boot a system via CD/DVD (knoppix for example).
> Mount small disk read-only 
> Mount bigger disk read-write
> 
> cd into mountpoint of the first one
> cp -a . ../<mountpoint_of_bigger_disk>
> 
> Seems to me slow but correct? Or?
> 
> (I have to set the bootable flag of the correct partion
> additionally...)
> 
> I dont want to have a booting system afterwards, which "runs" for --
> say -- three month and suddenly hit a obscure bug due to my
> copy-commands, which only did it to 99.87% correct... ;)
> 
> I would like to preserve as much as possible of the file/directoy
> times ,,,
> 
> Or does a mystical command with s-tar a better job faster? 
> 
> Thank you very much in adance for any help!

I like rsync and be sure to say --numeric-ids or whatever to retain the
same userids for permissions, but otherwise you are good to go.

-- 
Your life is like a penny.  You're going to lose it.  The question is:
How do
you spend it?

         John Covici
         covici@ccs.covici.com

[gentoo-user] Re: Moving the system from one disk to another

[Kerin Millar]

On 04/04/2010 20:05, meino.cramer@gmx.de wrote:
>
> Hi,
>
> I have to move my whole system from one disk to another
> bigger one.
>
> I think of doing as follows:
> Boot a system via CD/DVD (knoppix for example).
> Mount small disk read-only
> Mount bigger disk read-write
>
> cd into mountpoint of the first one
> cp -a . ../<mountpoint_of_bigger_disk>
>
> Seems to me slow but correct? Or?

cp -a is fine although, in my experience, I've found that rsync is more 
reliable:

rsync -av /mnt/oldrootfs/. /mnt/newrootfs/.

Note that -a covers almost everything but you may need the following 
additional options depending on how your filesystem has been used:

-H = preserve hard link
-A = preserve ACLs
-X = preserve extended attributes (in in doubt, recommended)

Whichever way you go about it, ensure that no pseudo-filesystem or bind 
mounts are present within "/mnt/oldrootfs" at the time.

Cheers,

--Kerin

Re: [gentoo-user] Re: Moving the system from one disk to another

[Neil Bothwick]

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On Sun, 04 Apr 2010 20:35:11 +0100, Kerin Millar wrote:

> Whichever way you go about it, ensure that no pseudo-filesystem or bind 
> mounts are present within "/mnt/oldrootfs" at the time.

Use the -x option with rsync to stop it descending into other filesystems.


-- 
Neil Bothwick

Did you hear about the dyslexic devil worshiper?
He sold his soul to Santa!

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Re: [gentoo-user] Re: Moving the system from one disk to another

[Kacper Kopczyński]

Dnia 2010-04-04, o godz. 21:04:03
Neil Bothwick <neil@digimed.co.uk> napisał(a):

> On Sun, 04 Apr 2010 20:35:11 +0100, Kerin Millar wrote:
> 
> > Whichever way you go about it, ensure that no pseudo-filesystem or
> > bind mounts are present within "/mnt/oldrootfs" at the time.
> 
> Use the -x option with rsync to stop it descending into other
> filesystems.
> 
> 

AFAIK

"mount --bind / /somewhere" and rsync'ing /somewhere/ instead of / would
be more useful then "-x" option - stage1,2,3 has static /dev entries
which should also be copied. Since udev mounts it with tmpfs, rsync
with -x would skip those entries (static and from tmpfs).

I suppose you can ignore static /dev if you use initrd.

Since author of this thread wants to mount filesystem(s) of "the
system" from livecd of some kind, there is no point in using any of
ideas in this or previous email - there will be no other filesystems
mounted.

I often use that trick with /somewhere/ to backup live system from
laptop to external drive. But it does not work well with innodb...

man mount
man rsync

good luck

-- 
Kacper Kopczyński

[gentoo-user] Re: Moving the system from one disk to another

[Kerin Millar]

On 05/04/2010 00:51, Kacper Kopczyński wrote:
> Dnia 2010-04-04, o godz. 21:04:03
> Neil Bothwick<neil@digimed.co.uk>  napisał(a):
>
>> On Sun, 04 Apr 2010 20:35:11 +0100, Kerin Millar wrote:
>>
>>> Whichever way you go about it, ensure that no pseudo-filesystem or
>>> bind mounts are present within "/mnt/oldrootfs" at the time.
>>
>> Use the -x option with rsync to stop it descending into other
>> filesystems.
>>
>>
>
> AFAIK
>
> "mount --bind / /somewhere" and rsync'ing /somewhere/ instead of / would
> be more useful then "-x" option - stage1,2,3 has static /dev entries
> which should also be copied. Since udev mounts it with tmpfs, rsync
> with -x would skip those entries (static and from tmpfs).

Well, no, because my response was based on the fact that the duplication 
will be carried out from an alternate environment provided by a CD/DVD, 
as Meino clearly stated in the original post. Thus, bind mounts, 
pseudo-filesystems and chroots need not come into the equation 
whatsoever. Indeed, it's the very same concern that you express which 
resulted in my recommendation to avoid such shenanigans and keep it 
simple. Ergo, just mount the root filesystem - nothing else - and copy 
it as-is. Static /dev entries would be copied without issue, as would 
everything else. It really couldn't be simpler.

You post hinges on the notion that he would be performing the process 
while booted from the system he is duplicating, in which case your 
advice would, of course, be entirely sensible. Ergo, he would indeed be 
best advised to bind mount / to a temporary directory and use that as 
the source for the exact reasons that you mention. I personally would 
not recommend doing it under these circumstances but it can certainly be 
done (though I'd suggest dropping to runlevel 1 first).

Cheers,

--Kerin

[gentoo-user] Re: Moving the system from one disk to another

[walt]

On 04/04/2010 01:04 PM, Neil Bothwick wrote:
> On Sun, 04 Apr 2010 20:35:11 +0100, Kerin Millar wrote:
>
>> Whichever way you go about it, ensure that no pseudo-filesystem or bind
>> mounts are present within "/mnt/oldrootfs" at the time.
>
> Use the -x option with rsync to stop it descending into other filesystems.

This is directed to all of you gurus who replied to Meino's post:

Meino's unstated assumption is that his new (larger) disk is already formatted
(possibly partitioned?) before he copies the existing filesystem to it.

IIUC the new disk will then be unbootable until grub or equivalent is installed
on the new disk.  Does this seem correct, or not?

My instinct is to use dd to duplicate the entire old disk to the new (unformatted)
disk and then use gparted to twiddle it from there. (But I do love a puzzle ;o)

[gentoo-user] Re: Moving the system from one disk to another

[Kerin Millar]

On 05/04/2010 02:34, walt wrote:
> On 04/04/2010 01:04 PM, Neil Bothwick wrote:
>> On Sun, 04 Apr 2010 20:35:11 +0100, Kerin Millar wrote:
>>
>>> Whichever way you go about it, ensure that no pseudo-filesystem or bind
>>> mounts are present within "/mnt/oldrootfs" at the time.
>>
>> Use the -x option with rsync to stop it descending into other
>> filesystems.
>
> This is directed to all of you gurus who replied to Meino's post:
>
> Meino's unstated assumption is that his new (larger) disk is already
> formatted
> (possibly partitioned?) before he copies the existing filesystem to it.
>
> IIUC the new disk will then be unbootable until grub or equivalent is
> installed
> on the new disk. Does this seem correct, or not?

Absolutely correct. Two commands from the grub shell and job done :)

>
> My instinct is to use dd to duplicate the entire old disk to the new
> (unformatted)
> disk and then use gparted to twiddle it from there. (But I do love a
> puzzle ;o)

In general, I'm a proponent of copying filesystems, as opposed to 
copying entire block devices or disks. That's not to say that there 
aren't some situations where the latter approach makes sense.

Note that it's possible to copy just the portion of the first sector 
that contains bootloader code as thus:

   dd if=/dev/sda of=/dev/sdb bs=446 count=1

NOTE: that's 446 as opposed to 512 as the latter would result in the 
partition table being copied too, which would be most undesirable.

Cheers,

--Kerin

Re: [gentoo-user] Re: Moving the system from one disk to another

[Neil Bothwick]

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On Sun, 04 Apr 2010 18:34:27 -0700, walt wrote:

> My instinct is to use dd to duplicate the entire old disk to the new
> (unformatted) disk and then use gparted to twiddle it from there. (But
> I do love a puzzle ;o)

This works but has a some disadvantages. First, it is very slow. Then you
copy all filesystems as-is, including any fragmentation (which may be
significant if the old disk is nearly full). Also, rearranging the
partitions can be extremely time consuming, and not that straightforward
if you are moving partition start points.

A different sized disk generally deserves a different partition layout, so
starting from scratch and copying only the data is a better option.

You can also substantially reduce downtime by first rsyncing while the
system is running (using either -x or bind mounts). That will give a
slightly inconsistent root, so you then repeat the process from a live CD
(using --delete with rsync) to clean things up. The latter rsync takes a
fraction of the time as 99.*% of the data is already cpied.


-- 
Neil Bothwick

C&W music backward: get yer dog, wife, job, truck, kids, and sobriety
back.

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Re: [gentoo-user] Re: Moving the system from one disk to another

[Neil Bothwick]

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On Mon, 5 Apr 2010 12:01:28 +0100, Mick wrote:

> > You can also substantially reduce downtime by first rsyncing while the
> > system is running (using either -x or bind mounts). That will give a
> > slightly inconsistent root, so you then repeat the process from a
> > live CD (using --delete with rsync) to clean things up. The latter
> > rsync takes a fraction of the time as 99.*% of the data is already
> > cpied.  
> 
> I don't know how slow rsync is the first time you run it. Since no one
> has yet suggested it star may be faster, while tar would do it nicely
> like so:

The speed is about the same. It's slow the first time because you have to
copy several gigabytes of data, whichever method you use. The advantage
of rsync is that you can do this while the system is still running then
do a quick update while booted from the live CD, massively reducing
downtime.


-- 
Neil Bothwick

Top Oxymorons Number 24: New classic

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Re: [gentoo-user] Moving the system from one disk to another

[Dale]

meino.cramer@gmx.de wrote:
> Hi,
>
> I have to move my whole system from one disk to another
> bigger one.
>
> I think of doing as follows:
> Boot a system via CD/DVD (knoppix for example).
> Mount small disk read-only
> Mount bigger disk read-write
>
> cd into mountpoint of the first one
> cp -a . ../<mountpoint_of_bigger_disk>
>
> Seems to me slow but correct? Or?
>
> (I have to set the bootable flag of the correct partion
> additionally...)
>
> I dont want to have a booting system afterwards, which "runs" for --
> say -- three month and suddenly hit a obscure bug due to my
> copy-commands, which only did it to 99.87% correct... ;)
>
> I would like to preserve as much as possible of the file/directoy
> times ,,,
>
> Or does a mystical command with s-tar a better job faster?
>
> Thank you very much in adance for any help!
>
> Best regards,
> mcc
>    

The way you plan to do this is almost exactly what I have done several 
times in the past.  I usually add the -v option so that I can tell about 
where the copy process is.  This is not a fast way according to some.  I 
have never compared this with using rsync, tar, star and all the rest.  
The biggest thing, make sure whatever you boot will access your drives 
with DMA and all the other goodies turned on and fully functioning.

When the copy process is done, install grub as well unless you plan to 
still use the old drive and do some editing on the fly.

Dale

:-)  :-)