GNU ddrescue

 GNU ddrescue. This is the best utility for grabbing data off a failing hard drive. It is fast for a dd-based command, and smart enough to skip over bad blocks and keep going, looking for good blocks to copy.

The most surefire method I know requires a second local hard drive of equal or greater size; either SATA/PATA or USB. Then boot up SystemRescue and copy the first drive to the second drive. Of course you must replace the drive names in the example with your own drive names:

# ddrescue /dev/sda /dev/sdb

You may copy partitions instead of whole drives. Then run fsck on the second drive to check for and fix errors. Make sure it is not mounted, then run this command:

# fsck /dev/sdb

Add the -a option to tell fsck to automatically fix all errors. Use fsck only on Linux filesystems. For other filesystems you'll need their own native filesystem-consistency-fixing utilities.

Don't confuse GNU ddrescue with dd-rescue. They do the same thing and both do it well, but I think ddrescue is faster and more reliable.

GParted is the best partitioning and filesystem-creation application there is. Put it on a bootable medium and you can manage most Linux, Unix, Mac OS X, or Windows partitions and filesystems. Add the dd-based Clonezilla for cloning, and you have the ultimate power tool for new installations, restores, and replications. Clonezilla is an intelligent partition or disk-cloning program that works on any filesystem, because it operates at the block level. On supported filesystems (which are pretty much the same batch as GParted) it copies only used sectors. On unsupported filesystems it can't tell which ones are used, so it does a block-by-block copy. Either way you get your clones.

Fixing Horked MBRs

When you're multi-booting or installing a new operating system onto a used system, sometimes the MBR (Master Boot Record) gets all messed up, so you need to wipe it out and start over. You can do this with the dd command. Be sure to use your own drive name for the of= value:

# dd if=/dev/zero of=/dev/hda bs=446 count=1

That preserves the partition table. If you also want to zero out the partition table, do this:

# dd if=/dev/zero of=/dev/hda bs=512 count=1

S: backup boot partition, bootsector

Usage

        # save MBR
        dd if=/dev/hda of=/export/sysbaks/hda-img.mbr bs=512 count=1
        dd if=/dev/hdb of=/export/sysbaks/hdb-img.mbr bs=512 count=1

        # save C: boot
        dd if=/dev/hda3 of=/export/sysbaks/hda-img.btc bs=512 count=1
        dd if=/dev/hdb3 of=/export/sysbaks/hdb-img.btc bs=512 count=1

Help

you can use lilo.conf specifying the boot partition or you can simply use dd to work with bootsectors. for example, to make a backup copy of a bootsector in a partition, say, hda1, you could do:

dd if=/dev/hda1 of=bootsect.hda1 bs=512 count=1

if you want to recover later you do:

dd if=bootsect.hda1 of=/dev/hda1 bs=512 coount=1

in the same way you could copy hda1 bootsector to hda2 bootsector:

dd if=/dev/hda1 of=/dev/hda2 bs=512 count=1

Patrick Machado

Ghost Linux

Newsgroups: comp.os.linux.misc
 

> Does anyone know of a program that will ghost Linux in the same way as
> Norton Ghost works in Windows?

Yes , Ghost will work. I use Ghost to ghost machines with Linux and Windows preinstalled.

Rafael

Ghost Linux

cpio? afio? tar? These are archiving programs, and work at the filesystem level (meaning they're not quite like Ghost, but they're still excellent for backing up data.)

If you want to make an "image backup" then you use dd. dd works at the raw device level, making a sector-by-sector copy of a disk. You can make an exact copy of a hard disk by doing: dd if=/dev/hda of=somewhere bs=8192
which copies everything on the hard disk at /dev/hda to "somewhere". "somewhere" can be on a remote server, naturally. You should bzip2 it once it's there, to reduce time taken by the next step.

You can re-create the original image on /dev/hda by booting from a Linux floppy that has enough smarts to mount the remote server via NFS or Samba and also has bunzip2 and dd. This Linux boot floppy would do something very similar to:
mount -t smb //remoteserver/images /mnt dd if=/mnt/linuxhdaimage.bz2 | bunzip2 -dc | dd of=/dev/hda

There's got to be a better way to do that, though. "rsync" would not chew up nearly so much network bandwidth, but it might have problems with things that require absolute positioning on disk like the MBR, the kernel image, and the loading map. I suppose you could combine the approaches, using dd to recover the MBR and /boot, then using rsync to fix everything else. This would require a separate /boot partition, naturally, but most people have that.

Please note that I have never tried the more complex versions of this. I did use dd and a bootdisk to back up and restore my entire laptop once, but that was it. Take with several grains of salt....

Matt G

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