Re: bsd disklabel and swap

From: Andries Brouwer (
Date: Fri Jul 04 2003 - 02:06:23 EST

On Fri, Jul 04, 2003 at 02:17:20PM +1000, Daniel Cavanagh wrote:

> i'm having a problem with a bsd disklabel and swap.
> my /dev/hda disk look like this
> partition 1: fat
> partition 2: ext2
> partition 3: openbsd
> it is a standard bsd disklabel with a as root and b as swap. this means
> that /dev/hda6 should be the swap partition. but "swapon /dev/hda6"
> prints "swapon: /dev/hda6: Invalid argument". it also prints that for
> any other valid partition. if i put this in /etc/fstab, on boot the
> kernel will print "Unable to find swap-space signature" before swapon
> prints the above message. but if i use /dev/hda3 instead, swapon will
> accept it and add a 512Mb swap, which is the correct size. but it
> appears that rather than writing at the start of the swap it starts
> writing at the start of the openbsd partition so my root partition is
> being corrupted. have i screwed or have you guys screwed up?

This sounds like user confusion.

A partition becomes a Linux swap partition by writing "SWAPSPACE" somewhere
at the beginning. (Yes, I know the details, don't tell me.)
If this signature is missing, the kernel refuses to swap to
the partition, in order to protect your data in case of a typo
in the swapon command.
The signature is written by the mkswap(8) command. Use it.


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