On 20100313_144620, Stephen Powell wrote: > On Sat, 13 Mar 2010 00:26:58 -0500 (EST), Paul E Condon wrote: > > > > A bit worrisome to me. UUID must be persistent during normal life of a > > device, so it can be used as an identifier. > > It is important to distinguish between a device and a partition. > /dev/hda is a device. /dev/hda1 is a partition. Partitions > can be created, deleted, moved, resized, reformatted, etc. many > times during the life of its containing device. The UUID of a > partition is assigned when the partition is formatted, either with > mkfs or mkswap. It retains this value until it is formatted again, > at which time a new UUID is calculated. I don't know what the > algorithm is for computing a UUID for a hard disk partition. > Of course, reformatting a partition destroys all data on it; so in > that sense it starts a new life with a new identity. >
I'm learning. One thing I discovered today is that in extN, a disk label (i.e. what you see when you type ls /dev/disk/by-label ) can have multiple values on a single disk. This label is stored in the partition table data of the several partitions. I haven't yet discovered what is done with the excess volume labels, or what, if any, confusion results from having multiple values. So ... its not quite true that there is a device and a partition. I know its a 'distinction without a difference', this sort of thing is confusing when one is trying to figure stuff out from incomplete information. Also, both mke2fs and tune2fs are capable of setting the UUID of a partition, either to a software computed value or a user supplied value. And dumpe2fs -h or tune2fs -l will display the UUID setting along with other partition parameters. Some things that I firmly believed a few hours ago, I now know are absolutely not true. What I will firmly believe a few hours from now remains to be seen. Thanks. -- 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/20100313230422.gd2...@big.lan.gnu