what is going on with "/dev/dm"

[Gene Czarcinski]

Oops ... do we have a new "feature"?  I do not like this one.

Whereas, the results of "df" was something of the form:
/dev/mapper/<whatever>

I am now getting on my f12 alpha/rawhide sytem:
/dev/dm-<number>

Doing a little search of the mailing list archives, I find the entry dated 
around 2 July:

================================================================================
 e2fsprogs-1.41.4-12.fc11 (FEDORA-2009-7278)
 Utilities for managing ext2, ext3, and ext4 filesystems
--------------------------------------------------------------------------------
ChangeLog:

* Wed Jun 24 2009 Eric Sandeen <sandeen(a)redhat.com&gt; 1.41.4-12
- blkid: use /dev/mapper/<name> vs /dev/dm-<N> (#497259)
* Thu Jun 18 2009 Eric Sandeen <sandeen(a)redhat.com&gt; 1.41.4-11
- Update journal backup blocks in sb after resize (#505339)
- Fix memory leak in extent handling functions
--------------------------------------------------------------------------------
References:

  [ 1 ] Bug #505339 - error still found with fsck after resizing during live 
image creation
        https://bugzilla.redhat.com/show_bug.cgi?id=505339
  [ 2 ] Bug #507461 - blkid returns dm-* for UUIDs instead of /dev/mapper name
        https://bugzilla.redhat.com/show_bug.cgi?id=507461
  [ 3 ] Bug #497259 - F10-F11: /dev/dm-N devices cause loss of all rescue 
ability
        https://bugzilla.redhat.com/show_bug.cgi?id=497259
-------------------------------------------------------------------------------

Is this new "feature" something we are going to have to live with??

Gene

what is going on with "/dev/dm" [important!]

[Gene Czarcinski]

On Friday 25 September 2009 16:15:32 Gene Czarcinski wrote:
>  Oops ... do we have a new "feature"?  I do not like this
> one.
>  
>  Whereas, the results of "df" was something of the form:
>  /dev/mapper/<whatever>
>  
>  I am now getting on my f12 alpha/rawhide sytem:
>  /dev/dm-<number>
>  
>  Doing a little search of the mailing list archives, I find the entry dated
>  around 2 July:
>  
>   
===========================================================================
>  ===== e2fsprogs-1.41.4-12.fc11 (FEDORA-2009-7278)
>   Utilities for managing ext2, ext3, and ext4 filesystems
>  ---------------------------------------------------------------------------
>  ----- ChangeLog:
>  
>  * Wed Jun 24 2009 Eric Sandeen <sandeen(a)redhat.com&gt; 1.41.4-12
>  - blkid: use /dev/mapper/<name> vs /dev/dm-<N> (#497259)
>  * Thu Jun 18 2009 Eric Sandeen <sandeen(a)redhat.com&gt; 1.41.4-11
>  - Update journal backup blocks in sb after resize (#505339)
>  - Fix memory leak in extent handling functions
>  ---------------------------------------------------------------------------
>  ----- References:
>  
>    [ 1 ] Bug #505339 - error still found with fsck after resizing during
>   live image creation
>          https://bugzilla.redhat.com/show_bug.cgi?id=505339
>    [ 2 ] Bug #507461 - blkid returns dm-* for UUIDs instead of /dev/mapper
>   name https://bugzilla.redhat.com/show_bug.cgi?id=507461
>    [ 3 ] Bug #497259 - F10-F11: /dev/dm-N devices cause loss of all rescue
>  ability
>          https://bugzilla.redhat.com/show_bug.cgi?id=497259
>  ---------------------------------------------------------------------------
>  ----
>  
>  Is this new "feature" something we are going to have to live with?? 

I believe that we cannot live with this ... or at least anaconda cannot:
https://bugzilla.redhat.com/show_bug.cgi?id=525912

Gene

what is going on with "/dev/dm" [important!]

[Christoph Frieben]

2009/9/27 Gene Czarcinski

>  Is this new "feature" something we are going to have to
> live with??
>
>   I believe that we cannot live with this ... or at least anaconda cannot:
>
>  https://bugzilla.redhat.com/show_bug.cgi?id=525912
>
>  Gene
>  
Fixed in Fedora-rawhide as of 2009-09-25. ~C

what is going on with "/dev/dm" [important!]

[Gene Czarcinski]

On Sunday 27 September 2009 06:21:49 Christoph Frieben wrote:
>  2009/9/27 Gene Czarcinski
>  
>  > Is this new "feature" something we are going to have to live with??
>  >
>  >  I believe that we cannot live with this ... or at least anaconda cannot:
>  >
>  > https://bugzilla.redhat.com/show_bug.cgi?id=525912
>  >
>  > Gene
>  
>  Fixed in Fedora-rawhide as of 2009-09-25. ~C
>   
Confirmed by testing with:
http://alt.fedoraproject.org/pub/alt/stage/12-Beta-TC/Fedora-12-Beta-TC-
x86_64-DVD/Fedora-12-Beta-x86_64-DVD.iso

525912 has been closed.

I am still a bit puzzled with the /dev/dm-N situation.  I have read the 
comments in Bug #507461 and Bug #497259 and am a bit unclear why /dev/dm-N 
shows up.  As I understand it, Fedora maintainers/developers are doing 
something to suppress it.  Is this something from upsteam?  Why?

IMHO, having something show as /dev/dm-1 is not as meaningful as 
/dev/mapper/VGx-root (such as in the output of "df").  If this is the result 
of upstream stuff, how do other distributions such as debian handle it?

Gene

what is going on with "/dev/dm" [important!]

[Richard Ryniker]

> I am still a bit puzzled with the /dev/dm-N situation.  I have read
> the 
> comments in Bug #507461 and Bug #497259 and am a bit unclear why /dev/dm-N 
> shows up. 
In F11, if /etc/fstab contains an entry where a logical volume is denoted
by something like "/dev/mapper/vg_ryniker-lv_root" then that
identification appears when the mount command lists mounted filesystems.

If a logical volume is denoted by UUID, such as
"UUID=f46b989b-d781-420c-a064-386c85d7bc67", this mounted filesystem is
identified by something like "/dev/dm-2".

This observation may not apply to F12 (sorry, I cannot check that right
now); if it is true, this suggests a way to obtain the output format you
seek.