Groups > linux.debian.user > #197617

Re: BTRFS and debian

From	David Christensen <dpchrist@holgerdanske.com>
Newsgroups	linux.debian.user
Subject	Re: BTRFS and debian
Date	2018-07-14 03:00 +0200
Message-ID	<wbh4J-36K-1@gated-at.bofh.it> (permalink)
References	(2 earlier) <wasbT-6Ry-9@gated-at.bofh.it> <waA9s-3fE-7@gated-at.bofh.it> <waCEh-4yC-3@gated-at.bofh.it> <waUUx-6QJ-5@gated-at.bofh.it> <wbeTf-1Ps-1@gated-at.bofh.it>
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On 07/13/18 15:36, Pascal Hambourg wrote:
> Le 13/07/2018 à 03:13, David Christensen a écrit :
>> file(1) -- no:
>>
>> 2018-07-12 17:55:01 root@po ~
>> # file /dev/sda1
>> /dev/sda1: block special (8/1)
> 
> You must add the option -s so that file looks into the special device 
> file contents.

2018-07-13 17:39:48 root@po ~
# file -s /dev/sda1
/dev/sda1: BTRFS Filesystem label "po_boot", sectorsize 4096, nodesize 
16384, leafsize 16384, UUID=6ff0dd1d-8d46-454b-bb35-a09afc47145a, 
65490944/999292928 bytes used, 1 devices

2018-07-13 17:39:51 root@po ~
# file -s /dev/sda2
/dev/sda2: data

2018-07-13 17:39:59 root@po ~
# file -s /dev/sda3
/dev/sda3: LUKS encrypted file, ver 1 [aes, xts-plain64, sha256] UUID: 
0152d2e2-4cfb-42c4-a121-6fb832962e47


The output for /dev/sda2 is not very informative (e.g. clues that it has 
dm-crypt, random key, and swap).


>> I have been using /dev/disk/by-id/* successfully [in /etc/crypttab] for a while, but 
> 
> Did the installer automatically wrote this in /etc/crypttab or did you 
> replace the original device name ?

I edited /etc/crypttab.


>> /dev/disk/by-partuuid sounds even better -- this will prevent 
>> confusion if and when I move partitions or images to other devices.
> 
> Beware that unlike a UUID or LABEL, a PARTUUID or PARTLABEL is stored in 
> the partition table, not in the partition data.
> Also note that a DOS partition table entry does not contain a UUID nor 
> LABEL, and the PARTUUID is artificially built by combining the 32-bit 
> "disk identifier" field in the MBR and the partition number. So if the 
> partition number or the disk identifier changes, the PARTUUID changes.
> 
> In short :
> - if you move the disk contents (including the partition table) to 
> another disk, the PARTUUID is preserved ;
> - if you move the partition contents to another partition, the PARTUUID 
> is not preserved.

Thanks for the warning.  My typical use-case is to move the entire 
system drive image between various 16+ GB devices, so PARTUUID should work.


> There is a hackish way to add a UUID to a plain dm-crypt partition : 
> write metadata of any kind at the beginning of the partition (ext2, 
> swap, LUKS...) and specify an offset for dm-crypt data beyond the metadata.

Okay.


David

Thread

BTRFS and debian Ge <gpdsbe@mailbox.org> - 2018-07-09 20:20 +0200
  Re: BTRFS and debian Matthew Crews <mailinglists@mattcrews.com> - 2018-07-09 21:40 +0200
    Re: BTRFS and debian Ulf Volmer <u.volmer@u-v.de> - 2018-07-09 22:00 +0200
      Re: BTRFS and debian Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-07-09 23:00 +0200
        Re: BTRFS and debian Ulf Volmer <u.volmer@u-v.de> - 2018-07-09 23:10 +0200
      Re: BTRFS and debian Matthew Crews <mailinglists@mattcrews.com> - 2018-07-09 23:40 +0200
  Re: BTRFS and debian David Christensen <dpchrist@holgerdanske.com> - 2018-07-10 05:40 +0200
    Re: BTRFS and debian Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-07-11 20:40 +0200
      Re: BTRFS and debian David Christensen <dpchrist@holgerdanske.com> - 2018-07-12 05:10 +0200
        Re: BTRFS and debian Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-07-12 07:50 +0200
          Re: BTRFS and debian David Christensen <dpchrist@holgerdanske.com> - 2018-07-13 03:20 +0200
            Re: BTRFS and debian Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-07-14 00:40 +0200
              Re: BTRFS and debian David Christensen <dpchrist@holgerdanske.com> - 2018-07-14 03:00 +0200
                Re: BTRFS and debian Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-07-14 11:10 +0200
                Re: BTRFS and debian David Christensen <dpchrist@holgerdanske.com> - 2018-07-14 21:40 +0200
                Re: BTRFS and debian Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-07-14 23:10 +0200
            Re: BTRFS and debian Zenaan Harkness <zenaan@freedbms.net> - 2018-07-14 01:40 +0200
    Re: BTRFS and debian David Wright <deblis@lionunicorn.co.uk> - 2018-07-12 20:00 +0200
      Re: BTRFS and debian David Christensen <dpchrist@holgerdanske.com> - 2018-07-13 05:00 +0200
        Re: BTRFS and debian Dan Ritter <dsr@randomstring.org> - 2018-07-13 12:00 +0200
          Re: BTRFS and debian <tomas@tuxteam.de> - 2018-07-13 12:30 +0200
          Re: BTRFS and debian David Christensen <dpchrist@holgerdanske.com> - 2018-07-14 03:10 +0200
        Re: BTRFS and debian Zenaan Harkness <zenaan@freedbms.net> - 2018-07-14 01:40 +0200
          Re: BTRFS and debian David Christensen <dpchrist@holgerdanske.com> - 2018-07-14 03:10 +0200
            Re: BTRFS and debian Zenaan Harkness <zenaan@freedbms.net> - 2018-07-14 12:00 +0200
              Re: BTRFS and debian Reco <recoverym4n@gmail.com> - 2018-07-14 12:30 +0200
                Re: BTRFS and debian Zenaan Harkness <zenaan@freedbms.net> - 2018-07-14 12:40 +0200
              Wrapping lines, was Re: BTRFS and debian David Wright <deblis@lionunicorn.co.uk> - 2018-07-15 05:20 +0200
                Re: Wrapping lines, was Re: BTRFS and debian Zenaan Harkness <zenaan@freedbms.net> - 2018-07-15 05:30 +0200
                Re: Wrapping lines, was Re: BTRFS and debian Zenaan Harkness <zenaan@freedbms.net> - 2018-07-15 12:30 +0200
        Re: BTRFS and debian Zenaan Harkness <zenaan@freedbms.net> - 2018-07-14 11:40 +0200

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