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Re: Understanding LVM UUIDS



On 06/23/2010 09:47 AM, Camaleón wrote:
> On Wed, 23 Jun 2010 09:40:22 +0100, Alan Chandler wrote:
>> I feel I should move my entire /etc/fstab over to using uuids
> 
> Mmm... any strong reason for doing that? :-)

Whether or not these are his reasons, I can tell you why that is a wise
move. UUIDs are unique to the device/filesystem. The major advantage of
using UUIDs is that you don't have to worry about reordering of disks by
the kernel when it sees it in a different order than previous.


> I'm with Lenny and the old naming method ("/dev/sdx") is the default for 
> "/etc/fstab".

This isn't recommended, because if the Linux kernel developers change
drivers, and the drives become a new device (just as it happened when
ditching the PATA driver for SATA, and /dev/hda became /dev/sda), your
partitions/volumes won't mount. Instead, you should either be using
LABELs or UUIDs.

>> if I look in /dev/disk/by-id I can locate the following
>> and in /dev/disk/by-uuid (again excuse the word wrap)
>>
>> lrwxrwxrwx 1 root root 10 Jun 21 19:20
>> f3408fda-0649-414f-8446-c01cf4e07558 -> ../../dm-0
>>
>> There seems to be no correspondence between them

If you're running LVM2, then you need to be familiar with the LVM
commands. In particular, lvdisplay:

# lvdisplay
  --- Logical volume ---
  LV Name                /dev/work/root
  VG Name                work
  LV UUID                M5qcO0-CEBb-rn7M-tm2o-pgII-0HmE-LNuSW9
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                18.80 GiB
  Current LE             4813
  Segments               2
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           254:0

-- 
. O .   O . O   . . O   O . .   . O .
. . O   . O O   O . O   . O O   . . O
O O O   . O .   . O O   O O .   O O O

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