[CentOS] Boot message about "resume device"

Tom H wrote:
> On Sun, Aug 1, 2010 at 1:28 PM, Edward Diener <eldiener at tropicsoft.com> wrote:
>> When I boot CentOS 5.5, I receive the message:
>>
>> Unable to access resume device ( UUID = some UUID etc. )
>>
>> How do I find out what actual device to which this UUID refers ? It does
>> not appear to be a block device since it does not show when I try 'blkid'.
>> To what does "resume device" refer ?
>>
>> The boot succeeds but I would like to know what this messages means.
> 
> UUID?! "resume" must be set to that UUID in /init in your initrd.
> Updating/recreating your initrd should fix this problem.

How does one "update/recreate" the initrd image ?

Why would initrd hard-code a partition UUID ? If the UUID changes, which 
it has in my case when I had to move and reformat the swap partition, 
then the initrd image is now wrong.