If you are using count=, that overrides leaving out notrunc. So then, you would make a complete backup file, and chop it up in small pieces with the count option.

It is probably something in the surplus sectors at the end of the disk that is dd resistant. Read about surplus sectors in my original post. Then, overwrite them with random characters. If that doesn't work, make a file the size of the surplus sectors, and write the file in one block to the surplus sectors.

Thanks for the tip! I'm just a little unclear as to how this will work since (as I said before) I'm trying to backup 18GB of data to my 10GB HDD, so would I use dd like this:

First to make the full clone files without the empty space:

dd if=/dev/hda1 of=/mnt/mydir/hda1_piece1_7-15-2006.ddclone bs=4096 conv=noerror

dd if=/dev/hda1 of=/mnt/mydir/hda1_piece2_7-15-2006.ddclone bs=4096 skip=[however many records already written] conv=noerror

And then to split up the clone files to fit them on (in this case) DVDs:

dd if=/mnt/mydir/hda1_piece1_7-15-2006.ddclone of=/mnt/otherdir/hda1_chunk1_7-15-2006.ddclone bs=4096 count=[4.7GB] conv=noerror

dd if=/mnt/mydir/hda1_piece1_7-15-2006.ddclone of=/mnt/otherdir/hda1_chunk2_7-15-2006.ddclone bs=4096 count=[4.7GB] skip=[4.7GB] conv=noerror

...and so on...

Would that do it?

Thanks for all your help, Awesome!

Did you try to dd from a live distro instead from inside ubuntu.
This may avoid the seg fault (I think it did at home once, not 100% sure)

Problem solved !

In fact windows was identifying my new disk as F: because its disk signature appears in the registry to refer to F:.

The solution was to get the signature of my old disk and replace the signature of my new disk with it in the MBR. A bit more on disk signature can be found on wikipedia's article on MBR (I don't put the link because I'm too "young" on this forum to have this right).

Thanks again.
I've learned a lot on partitionning and windows boot process this week-end

olivier

First:
dd if=/dev/hda1 of=/some-directory-not-on-hda1/complete-image-of-hda1.bin

Then:
dd if=/some-directory-not-on-hda1/complete-image-of-hda1.bin bs=1M count=4200 of=/some-directory/DVD-image-of-hda1-1.bin conv=noerror
dd if=/some-directory-not-on-hda1/complete-image-of-hda1.bin bs=1M skip=4200 count=4200 of=/some-directory/DVD-image-of-hda1-2.bin conv=noerror
dd if=/some-directory-not-on-hda1/complete-image-of-hda1.bin bs=1M skip=8400 count=4200 of=/some-directory/DVD-image-of-hda3-1.bin conv=noerror...

If you can't figure this out from my previous post, which said, "First make a complete image, and then chop it up in DVD size pieces with count, I don't think it is safe for you to have your data rely on dd. You might be better of with a backup program that is made for imaging onto DVD's.

You're pretty smart, and a fairly good writer. What you cited as the cause and solution don't add up, though. Where you using two different size disks, and overwrote the partition table of one with the other, and then did you redo the entire MBR again? Or did you patch in just four bytes at 0x1b8 as the post implies? I would like everyone to know how this actually worked, because if it is as you imply, that you patched in four bytes and this solved the whole problem, it is worthy of further investigation. Why don't you tell us, in your own words, the steps you took to solve this problem, in a little more detail.

Tom

I'm not sure my previous emails were clear, as the story has been cut into pieces.
Not knowing exactly what was confusing, here is the complete story:

- Hard drives:
1- old 40Gb formatted/partitionned with partition magic
hosting Windows XP home and Mandrake 9.1
starts making noise

2- new 80Gb formatted/partitionned using the same partition magic from my old windows
(40Gb is main disk, 80Gb plugged through usb)
I create identical partitions to make things simple,
plus one big ext3 for future use (Ubuntu).

- After partitionning:

1- Ubuntu installed on 80Gb (which now replaces 40Gb inside my laptop).

2- Use dd to copy each partition separately from 40Gb (temporarily connected through usb).
All my files are there. No problem (even if dd terminates with a segfault).

3- Update my Grub config file to tell how to start with copy of windows and copy of Mandrake.

4- Try rebooting under Mandrake and Windows (40Gb unplugged):
- Mandrake fine.
- Windows stops with blue "login" screen, a working mouse, but no user.

5- Investigate a lot on windows startup sequence and stuff.
Try cleaning "surplus sectors" as advised.
This only leads to windows telling me that F: needs to be checked.
But why F: ?...

6- The new windows partition was F: when formatted by old windows, meaning that something not modified by dd tells windows my first partition is F: (something on the partition table or MBR ?).

7- Reading some documentation on the MBR, I discover the "disk identifier" and the fact that windows uses it for various stuff. I guess that "various stuff" covers "assigning drive letters to partitions".

8- So, I get the disk identifier of 40Gb and replace the disk identifier of 80Gb with it.
Now windows works from scratch as on my old 40Gb.


Does that answer your question ?
I guess this is not a usual problem since not everyone partitions under windows (to get the exact same partitions) before copying partitions with dd (because partitionning magic couldn't do it).

olivier

I understand that you can't clone a partition or device back onto itself. If you were confused by my post, let me assure you that what I meant by "/mnt/mydir" was "/some-directory-not-on-hda1/".

I understand all this too, and, except for the values of 'bs' and 'skip' you've specified in these commands, it's the same as in my post.

Forgive me for repeating myself, but I'm finding your answer a little hard to comprehend. Are you saying that there's no way to backup 18GB of raw data in uncompressed form to a 10GB HDD? Do I have to go out and buy a HDD with a capacity equal to or greater than the amount of data I want to backup? Is this process (which I tried to describe in my previous post and therefore won't show the commands here) possible or impossible to do:

Copy as much raw data to the smaller HDD as it can hold; burn DVDs of that data; skip over whatever data from 'if' that was already copied and copy the rest; burn the remaining data to DVDs.

I'm just trying to avoid having to buy another HDD. Can I do what I'm suggesting here (again, for the commands see my previous post)?

Thanks for your patience and help. I appreciate it.

Hey again. While waiting for an answer to my previous question, I went ahead and decided to test if I could backup the partition on my other PC using dd to backup only the used space on the partition. My 2nd PC is a Windows 98 PC with 2 10GB HDDs: /dev/hda which is my Windows partition w/ FAT32 and uses 4.5GB of space, and /dev/hdb which I use for backups and is empty at the moment. Unfortunately, I was unable to copy only the used space from /dev/hda1 to /dev/hdb1--every time I tried, I found that the file I was dumping /dev/hda1 to was 10GB instead of 4.5GB. Here's what I did:

First I simply tried

dd if=/dev/hda1 of=/some_directory_on_hdb1/clone.file bs=4096 conv=noerror

which copied all 10GB (empty space obviously included) into my clone file.

Next, I read back in this thread and saw that if that doesn't work, I should try creating a file in the empty space on my partition and fill it with zeroes. So, since FAT32 has a filesize limitation (which I forget) I made a series of 1GB zero-filled files until the empty space on /dev/hda1 was completely full, like this:

dd if=/dev/zero of=/some_directory_on_hda1/zerofil1.bin count=2097152

dd if=/dev/zero of=/some_directory_on_hda1/zerofil2.bin count=2097152

dd if=/dev/zero of=/some_directory_on_hda1/zerofil3.bin count=2097152

...and so on...

When the empty space was filled up, I deleted these zero-filled files and then attempted the same command I listed above... but again, dd copied every sector in the partition, not just the 4.5GB of actual data. I don't know what I did wrong, if anything, or if there may be some configuration file or something that presets dd's operations somehow, but could you tell me why this didn't work? I'd greatly appreciate any help.

Cheers!

Copy, please go find a backup program that will image your partition onto DVD's for you. Dd isn't going to work. I don't what you are actually doing, but it's not working. I can't help you. It's probably not your fault, so don't worry.

Olivier,

Thanks for the clarification.

Could it be the Linux distribution I'm using? I use a live-CD called Sysresccd version 0.2.19. Maybe I should try using a different live-CD. Which do you use and/or recommend? I *really* don't want to buy any more software or hardware if I don't have to (budget is an issue with me).

Thanks again.

Dd actually does copy all the zeroes even without conv=notrunc.

Its really a very good contribution!! I found it very usefull, any just now I have started working on this, I will be back whenever I have queries..