Arch Linux

Vladman

Member

Registered: 2009-01-28

Posts: 118

dd to a smaller drive

Not sure if this belongs in this forum, (mods, feel free to move).

I just did a dd of my current arch install from 250 gig drive to 150 gig and when I boot I get an error, something about super block being a diffrent size.
I tried googling the answer but no luck.

Can some one explain what I need to do to fix it?
Appreciate your help.

lilsirecho

Veteran

Registered: 2003-10-24

Posts: 5,000

Re: dd to a smaller drive

AFAICT your move by dd to smaller drive is not allowed.  The drive you transfer to with DD has to be the same size as the source drive (and maybe larger).

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Vladman

Member

Registered: 2009-01-28

Posts: 118

Re: dd to a smaller drive

Thanks, is there another way to do the same with maybe another program?

hbekel

Member

Registered: 2008-10-04

Posts: 311

Re: dd to a smaller drive

dd does only what you tell it to. It copies raw data from one file to another, be it a device node representing a complete drive (e.g. /dev/sda) or a partition (e,g, /dev/sda4), until that fails. It doesn't know anything about the data it copies, and it doesn't care. So it can't shrink or grow your filesystem or keep it consistent since it simply doesn't work that way. You effectively just cut off the last 100G of your hardrive. It's like cutting your laptop in two and throwing away one part to get a netbook

Use dd only to copy from/to partitions (or whole drives) that have the same size. you *can* copy to a larger partition/drive, but then you'd end up with unused space. It's been called the "data-destroyer" for a reason.

Use Gparted to shrink your source partition first, then create a partition on the smaller drive of the exact same size, and then you can use dd to copy from the source to the target partition. Be sure you know the difference between device nodes and partition nodes (e.g. /dev/sda vs /dev/sda1) before doing so.

grey

Member

From: Europe

Registered: 2007-08-23

Posts: 679

Re: dd to a smaller drive

Take a look at fsarchiver. You have to set up the partition table of the target device before restoring, but other than that it should just work.

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Vladman

Member

Registered: 2009-01-28

Posts: 118

Re: dd to a smaller drive

Thanks for your replyes guys, I appreciate it.
I'm going to take a look at fsarchaver.

vacant

Member

From: downstairs

Registered: 2004-11-05

Posts: 816

Re: dd to a smaller drive

I've moved arch root partitions loads of times, usually I boot an Arch install USB img and jiggle my partitions from there.

Is there a particular reason you can't just create the new file system on the smaller disk/partition, mount the current and new partitions, and cp -a?

Gen2ly

Member

From: Sevierville, TN

Registered: 2009-03-06

Posts: 1,529

Website

Re: dd to a smaller drive

You can gzip it.  It can be cut down by a good bit with large open spaces and the drive not being very full:

dd if=/dev/sda | gzip -9 > /mnt/disk2/backup.gz

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synthead

Member

Registered: 2006-05-09

Posts: 1,337

Re: dd to a smaller drive

What about opening your image in gparted?

gparted /path/to/image.img