On 20100313_020002, thib wrote: > Stephen Powell wrote: > >I believe a UUID is generated when the partition is "formatted", either with > >mkfs or mkswap. > > I confirm - just tried shrinking and growing back an extfs. UUID is > left untouched (as expected); that Mint article is BS or just > obsolete. > > -thib
A bit worrisome to me. UUID must be persistent during normal life of a device, so it can be used as an identifier. A copy of the UUID that is readable must be attached to the device, so that the device can be identified and distinguished from any other device. Either an arbitrary random number can be recorded on read-mostly-memory in the device, or some fixed data in the format of the device is used in conjunction with a message-digest algorithm to come up with a 32 hex digit id-number. And only fixed data on the device can be used. If the resulting 32hex digit number is not, itself, recorded in some hard to find place on the device. Your experiment shows that UUID is dependent on partition table data. Without bothering to check, I assert that it is not dependent on any other non-partition data that is saved on the device. If it were it wouldn't be persistent between reboots, etc. The number of bytes in a partition table is quite small and those bytes conform to a rather structured pattern, so there are far fewer independent patterns than 128 independent bits of partition record. In fact I would expect that name collisions are actually far more likely than one would expect from a simple-minded probability calculation. -- Paul E Condon pecon...@mesanetworks.net -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/20100313052658.ga2...@big.lan.gnu
