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I'm management a server that in /etc/fstab have references to some partitions using /dev/disk/by-id/DISK_ID-partN.

The server suddenly power-off and DISK_ID part of /dev/disk/by-id/DISK_ID-partN changed.

I always refer partition in /etc/fstab using UUID and will change the conf of fstab, but still I want know why the by-id change when tons of people on Internet said that such hard disk identifier don't change, even I read that OpenSuse use by-id in tis fstab.

Can partitions *UUID*s change too after a suddenly power-off? are *UUID*s less "mutable" than *by-id*s? I think that an explanation from where by-id come will help me to understand all this. I read that UUID is stored in the partition and just change its value after partition formatting, but not know much about by-id, just that udev is who generated-create it, but basing in what?

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What did it change from/to? The disk-id is normally taken from the disk hardware, so it won't change unless you physically replace the disk. –  psusi Jul 9 '13 at 2:44
@psusi I don't replace the disk between reboots. Those references are in fstab since months. I don't have now access to the server, but I don't think that old/new (from/to) values are relevant to my question. Anyway I could find new and old by-id values if you think could help to find out what happen. Anyway, someone that know udev deep enough could explain that ;) Thanks again for your comment. –  gsc-frank Jul 10 '13 at 0:17
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1 Answer


I am assuming the content of the partitions is still there and the UUID is the same.

Someone cloned the contents of the disk to a new one and replaced the disk.

UUIDs don't change when you duplicate a disk with dd (unlike disk/by-id) . They only change when you format a partition. [post number 3 in the linked discussion]

The disk might have been replaced due to several possible reasons:

  • SMART values have been deteriorating and to prevent loss of data on the respective disk it was cloned and replaced

  • disk was filling up and was replaced by a bigger one with same partition layout

  • disk was replaced due to speed reasons, e.g. HDD --> SSD

  • disk was replaced to obtain the original disk with it's data - for example as backup or evidence - but leave the system running.

Hope that helps!

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Welcome to Ask Ubuntu Tobias. Pls, allays read carefully the questions before reply. The disk was never replaced, the only event was a suddenly server power-off as I said in my question. I also stated in my question: "I read that UUID is stored in the partition and just change its value after partition formatting", so, seem to me that you don't ready my question at all. –  gsc-frank Aug 20 '13 at 19:56
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