dd and switching hard drives

DiddyWolf · n00b Joined: 13 Oct 2003 Posts: 4

I've read like 5-6 different articles about moving a gentoo install from one hard drive to another and all of them have said different things about dd.

My hard drive in my gentoo box started making clicking and whurring noises and i'm getting ready to move everything from that 7GB hard drive to a (hopefully) new 7-20GB hard drive (if/when i can find one. While i'm at it, any subjestions on where i can get one for cheep?).

My question is will dd copy the MBR or not and is this a good way to move from one hard drive to another? Also, are any other steps needed to get everything up and running on the new drive?

--DiddyWolf

TheCoop · Posted: Wed Feb 04, 2004 8:08 pm Post subject:

afaik 'dd if=/dev/hda dd=/dev/hdb' will copy the entire disk surface ie partition table, data and all. This is technically possible, and will work fine if you're lucky (YMMV), but its not recommended. The easiest way is probably to create the partitions on the new disk and then copy the data itself over (using methods in the forums, ie cp -axr or find . |cpio something)
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Jake · Veteran Joined: 31 Jul 2003 Posts: 1132

I would (and have in the past, actually) simply use the "cp -a" command and install the bootloader the traditional way (setup in the grub console or lilo after editing the config).

NeddySeagoon · Posted: Wed Feb 04, 2004 8:19 pm Post subject:

DiddyWolf,

Don't use dd to make a drive image unless you are going to restore it to an identical drive.

It will copy the MBR, partition tables and partitions quite literally, which may break on a drive with different geometry since a partition must start on head 0.
Any space on a bigger drive will also become unuseable, since the partition table will show the drive as fully used.

If you must use dd, make images of each partition to reinstall later. (tar would be better, provided you preserve permissions and timestamps)

Partition your new drive restore the partitions and reinstall the bootloader from scrach.
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Computer users fall into two groups:-
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those that have never had a hard drive fail.

Baldzius · Posted: Thu Feb 05, 2004 2:28 pm Post subject:

Never tried , but i would do that way:

1. Copy original MBR to another HDD
dd if=/dev/hda of=/dev/hdb bs=512 count=1
2. Make partitions, file systems
3. Not sure but as Jake said, i would give a try with cp command.

Can't try but really interested is this works?

NeddySeagoon · Posted: Thu Feb 05, 2004 6:36 pm Post subject:

Baldzius,

If cp can preserve permissions it will do in place of tar.

Why preserve the MBR?
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NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

Baldzius · Posted: Fri Feb 06, 2004 6:40 am Post subject:

flowctrl · n00b Joined: 18 May 2003 Posts: 53 Location: Banff, Canada

Large recursive copies can totally thrash a filesystem. I'm not sure why, but I've seen inodes get completely scrambled when doing large recursive cp. The best way to do it is to use dump/restore, or if the filesystem that you're using doesn't have dump/restore (like reiserfs), then use tar.

Examples: