Accuracy of sizes in partition work

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Accuracy of sizes in partition work

Postby rustleg » Fri Dec 09, 2011 3:02 pm

I am concerned about how accurate the size information is in Partition work. If I keep a record of the size and position of each partition in a drive using MB's from the BIBM screen can I reconstruct those partitions exactly via BIBM if the drive is trashed for example by a bad install of some system?

By way of further explanation I keep information similar to the list below which would represent the whole drive space:

BIBM 8 BootitEMBRM
Win7 25000 NTFS
----- 26482 Free space
Mint11 9994 ext4
Swap 2000 Linux Swap
W7Virtual 5994 NTFS

I am conscious that these figures may be approximations rather than true megabytes (or mebibytes whatever). Some of these partitions may have been positioned by butting up against other partitions which have since been deleted, so just recreating them from these numbers might perhaps not get them in exactly the same place as before. This is important in Linux systems which use UUIDs to define the partitions.
Russell
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Re: Accuracy of sizes in partition work

Postby DrTeeth » Fri Dec 09, 2011 4:23 pm

I may be missing something, but why not just backup the whole disk
using IfD with BING?

Though I am not a Linux maven by any means, I do have 5 distros
installed here and have never had problems restoring. Admittedly, if I
do restore over the existing partition. AIUI, there is no problem
restoring to a different location as UUIDs are for internal Linux use
only and do not denote location on a given HD.
--

Cheers

DrT
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Re: Accuracy of sizes in partition work

Postby rustleg » Sat Dec 10, 2011 8:53 am

DrTeeth wrote:I may be missing something, but why not just backup the whole disk
using IfD with BING?

I'm a bit surprised you recommend this approach. Some parts of the disk don't need backup, so backing up the whole disk each time I need a backup would create huge files and take a long time. I prefer to back up partitions which contain different OS's individually because the need for backup arises at different times for different systems and this saves time and space and is easier to organise and document. Also reinstating one wouldn't mess up any others in use.

DrTeeth wrote:AIUI, there is no problem
restoring to a different location as UUIDs are for internal Linux use
only and do not denote location on a given HD.

Thanks for this info. I assumed that the UUID must contain location information. I have tried a number of times to google for the UUID basis in Linux but failed. If the UUID is stored on the partition (perhaps in the superblock?) and is therefore searched for then perhaps partitions may be run successfully in different locations with the same UUID. I had blindly assumed that the OS had to recalculate the UUID somehow for each partition and then compare it to the fstab table entry, clearly I don't understand UUIDs. I did have trouble relocating partitions with Debian Linux when the "Squeeze" version came out with the Grub2 bootloader, I ended up having to reinstall from scratch. Perhaps this was more down to Grub than the use of UUIDs.

I think my question may still be relevant if Grub would be upset by a change of location. I seem to remember that when I tell an install to put the bootloader in the partition rather than the MBR there's usually a response to the effect that this is a BAD IDEA (their capitals not mine) - something to do with blocklists, I presume this is a list of the disk blocks relating to the partition which is therefore location dependent. Perhaps this is why they say it's a bad idea, but there's no choice for us as Bing must sit in the MBR.
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Re: Accuracy of sizes in partition work

Postby DrTeeth » Sat Dec 10, 2011 10:32 am

I have never seen that 'bad idea' message about installing grub in /.
In fact, this was the default location for Open SuSE12.1.
I only mentioned the whole disk backup as you seemed to be concerned
about the absolute location of partitions. I never do this myself and
like you, only backup OSs. In pre-UUID days, I used to have one swap
file for all my Linux installs. Now I have a separate swap file for
each one and back it up - AIUI - a Linux install can only use the swap
with the 'correct' UUID.
--

Cheers

DrT
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Re: Accuracy of sizes in partition work

Postby rustleg » Sat Dec 17, 2011 11:51 am

Re my original question
I wrote:If I keep a record of the size and position of each partition in a drive using MB's from the BIBM screen can I reconstruct those partitions exactly via BIBM?
I'd appreciate an answer from TB support please. I've wondered about this in the past many times and it would be good to know the answer.

DrTeeth wrote:I have never seen that 'bad idea' message about installing grub in /.
As to this just try googling for "GRUB BAD IDEA"

DrTeeth wrote: In pre-UUID days, I used to have one swap
file for all my Linux installs. Now I have a separate swap file for
each one and back it up - AIUI - a Linux install can only use the swap
with the 'correct' UUID.
i still use one swap for all my Linux systems and haven't come across any problem, if they do use a UUID you can discover it easily with the blkid command.
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Re: Accuracy of sizes in partition work

Postby TeraByte Support » Sat Dec 17, 2011 11:11 pm

No, you'd use something like mbrwork if you wanted to do that. But what
you'd normally do is "undelete" for standard partition types, or use the
"copy sectors" command in scripting to capture or replace the MBR (or more)
to/from a file.

"rustleg" wrote in message news:889@public.bootitbm...

Re my original question [quote="I":y3aw7tlu]If I keep a record of
the size and position of each partition in a drive using MB's from the BIBM
screen can I reconstruct those partitions exactly via BIBM?[/quote:y3aw7tlu]
I'd appreciate an answer from TB support please. I've wondered about this in
the past many times and it would be good to know the answer.

[quote="DrTeeth":y3aw7tlu]I have never seen that 'bad idea'
message about installing grub in /.
[/quote:y3aw7tlu]As to this just try googling for "GRUB BAD IDEA"

[quote="DrTeeth":y3aw7tlu]
In pre-UUID days, I used to have one swap
file for all my Linux installs. Now I have a separate swap file for
each one and back it up - AIUI - a Linux install can only use the swap
with the 'correct' UUID. [/quote:y3aw7tlu]i still use one swap for all my
Linux systems and haven't come across any problem, if they do use a UUID you
can discover it easily with the blkid command.

TeraByte Support
 
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