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Bug 271839 - false warning from mkswap in connection with device-mapper
Summary: false warning from mkswap in connection with device-mapper
Alias: None
Product: Gentoo Linux
Classification: Unclassified
Component: [OLD] Core system (show other bugs)
Hardware: All Linux
: High trivial (vote)
Assignee: Gentoo's Team for Core System packages
Depends on: 461382
  Show dependency tree
Reported: 2009-05-30 07:35 UTC by niteblade
Modified: 2013-03-11 12:12 UTC (History)
1 user (show)

See Also:
Package list:
Runtime testing required: ---


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Description niteblade 2009-05-30 07:35:24 UTC
From the mkswap manpage ("WARNING"):

mkswap refuses to erase the first block on a device with a disk label (SUN, BSD, ...) or on whole disk (e.g. /dev/sda).

This leads to a warning during boot with encrypted swap partitions using dmcrypt, since the encrypted partition looks like a whole disk (e.g. /dev/mapper/swap). 

I was a bit unsure about the Severity, since the swapspace actually works and this bug might as well be interpreted as "cosmetic". Maybe it is even enough to notify upstream about this.

Reproducible: Always
Comment 1 Wormo (RETIRED) gentoo-dev 2009-06-01 05:17:46 UTC
Thanks for the report. Even if no-one gets around to fixing it for a while, it is still useful to have it documented in the bug database so future users noticing the warning can know not to be concerned.
Comment 2 Nathan Caldwell 2009-08-10 04:12:33 UTC
I get the same thing, however the swap space is no longer mounted after the warning.

$ sudo /etc/init.d/dmcrypt restart
* WARNING: you are stopping a boot service
* Caching service dependencies...                                                           [ ok ]
* Removing dm-crypt mappings
* Removing dm-crypt mapping for: crypt-swap...                            [ ok ]
* Setting up dm-crypt mappings...
* Checking swap is not LUKS
* dm-crypt map crypt-swap...
* cryptsetup will be called with : -c aes -h sha256 -d /dev/urandom create crypt-swap /dev/system/swap                                               [ ok ]
*   Running pre_mount commands for crypt-swap...
mkswap: /dev/mapper/crypt-swap: warning: don't erase bootbits sectors
        on whole disk. Use -f to force.
$ free
             total       used       free     shared    buffers     cached
Mem:       4059344    2682836    1376508          0     150480     989128
-/+ buffers/cache:    1543228    2516116
Swap:            0          0          0
Comment 3 Samuli Suominen gentoo-dev 2013-03-11 12:09:44 UTC
I doubt this is a problem with device-mapper from current lvm2 package anymore.
If you still see this, please reopen this bug.