How to replace a hard drive...

[Christopher Browne]

On Thu, May 12, 2011 at 5:17 PM, Kevin Cozens <kevin-4dS5u2o1hCn3fQ9qLvQP4Q at public.gmane.org> wrote:
> Peter King wrote:
>>
>> Reboot, and the new disk
>> is seen by the BIOS; it finds grub on the MBR and loads it; I select a
>> kernel and start to
>> boot up -- by this time I'm starting to think it will work -- and then,
>> after it correctly
>> finds my keyboard, it just, well, stops. Nothing. No drive activity, no
>> indication of life.
>
> When I have copied files using rsync I include -S as one of the command line
> arguments.
>
>> Replacing the old disk I see that after finding a keyboard it then loads
>> /sys, and calls for
>> udev. Perhaps the problem is there.
>
> Recent Linux distros seem to want to use UUID strings in /etc/fstab to refer
> to the drives. Its all well and good until you change a partition or hard
> drive after which you find it fails to boot properly. Check your /etc/fstab
> file to see if it is using uuid strings rather than /dev/sdaN type partition
> specifiers.

Unfortunately, there's a dynamic here where the shift to UUIDs is
likely to be the better of the alternatives.

The trouble is that, with an burgeoning set of kinds of devices that
imagine themselves to be SCSI devices that appear as /dev/sd?, the
names of the devices have become rather less stable than you might
wish.

/dev/sda1 might assortedly be:
- A partition on a "USB stick"
- A partition on a SCSI disk
- A partition on a SATA disk on another bus
- A filesystem on a cell phone plugged into USB
- An iPod filesystem

If all of these things are plugged in at boot time, it may be pretty
unpredictable device gets tagged with /dev/sda, /dev/sdb, /dev/sdc,
and so forth, where having a UUID on the partition label will be the
more predictable thing.

I can imagine ways of trying to make things more predictable by, for
instance, having bus-named subdirectories under /dev, or by throwing
bus names into the device names.  I don't think it's obvious that this
*actually* stabilizes the names you need to stow in /etc/fstab; I
suspect that perceived stability is something of a mirage, and it's
certainly going to make device names more gibberishy.

I don't love UUIDs, but they may be the best of a bad lot :-(.
-- 
When confronted by a difficult problem, solve it by reducing it to the
question, "How would the Lone Ranger handle this?"
--
The Toronto Linux Users Group.      Meetings: http://gtalug.org/
TLUG requests: Linux topics, No HTML, wrap text below 80 columns
How to UNSUBSCRIBE: http://gtalug.org/wiki/Mailing_lists