[linux-lvm] how to change UUID of PV of duplicate partition (followup)

[Xen]

I mean,

This is what I mean:

   Found duplicate PV 3U9ac3Ah5lcZUf03Iwm0cgMMaKxdflg0: using /dev/sdb4 
not /dev/sdc4
   Using duplicate PV /dev/sdb4 without holders, replacing /dev/sdc4
   Volume group containing /dev/sdb4 has active logical volumes
   Physical volume /dev/sdb4 not changed
   0 physical volumes changed / 1 physical volume not changed

It immediately replaced the good PV with the bad PV (that I was trying 
to change) so I cannot actually get to the "bad" PV (which is duplicate) 
to change it without booting an external system in which I can effect 
one disk in isolation.

But, after running that command my root filesystem was now mounted 
read-only instantly so even just attaching the disk basically causes the 
entire system to instantly fail.

Real good right.

Probably my entire fault right :-/.

"Let's cause this system to crash, we'll attach a harddisk." "Job done!"

Actually I guess in this case it replaced the bad with the good but 
behind the scenes something else happened as well. This time it is 
hiding /dev/sdc4, the other time it was hiding /dev/sdb4, it seems to be 
random.

Basically any eSata system that a disk gets attached to could cause the 
operating system to fail. The same would probably be true of regular USB 
disks.

Even inserting a USB stick could crash a system like this.