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Groups > linux.debian.user > #274883 > unrolled thread
| Started by | Roger Price <debian@rogerprice.org> |
|---|---|
| First post | 2024-11-26 09:20 +0100 |
| Last post | 2024-11-26 16:30 +0100 |
| Articles | 5 — 4 participants |
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The "uniqueness" of UUIDs Roger Price <debian@rogerprice.org> - 2024-11-26 09:20 +0100
Re: The "uniqueness" of UUIDs Hans <hans.ullrich@loop.de> - 2024-11-26 10:00 +0100
Re: The "uniqueness" of UUIDs Roger Price <debian@rogerprice.org> - 2024-11-26 10:10 +0100
Re: The "uniqueness" of UUIDs George at Clug <Clug@goproject.info> - 2024-11-26 10:40 +0100
Re: The "uniqueness" of UUIDs Andy Smith <andy@strugglers.net> - 2024-11-26 16:30 +0100
| From | Roger Price <debian@rogerprice.org> |
|---|---|
| Date | 2024-11-26 09:20 +0100 |
| Subject | The "uniqueness" of UUIDs |
| Message-ID | <JMYXD-bIl2-1@gated-at.bofh.it> |
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Sorry, the formatting was messed up and the message unreadable. On Tue, 26 Nov 2024, George at Clug wrote: > "$ lsblk -f" output is very nice ! Thanks. I tried this and noticed UUID duplication in the output. I attach a small text file which shows what I saw. UUID sdg6 = UUID sdh6 ! NAME FSTYPE UUID ... ├─sdg6 linux_raid_membe3 f5e37a29-357a-e3f2-c731-e29eddce5e │ └─md3 ext4 1.039c24711-ab43-497c-bf3e-12b4032575a.4G ... ├─sdh6 linux_raid_membe3 f5e37a29-357a-e3f2-c731-e29eddce5e91 │ └─md3 ext4 39c39c24711-ab43-497c-bf3e-12b403257.4G If I wanted to retire /dev/sdg6 from the Raid array, I would not be able to use the UUID, only the unique SDxn. Aren't UUIDs supposed to be unique? Roger
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| From | Hans <hans.ullrich@loop.de> |
|---|---|
| Date | 2024-11-26 10:00 +0100 |
| Message-ID | <JMZAl-bIAy-3@gated-at.bofh.it> |
| In reply to | #274883 |
Am Dienstag, 26. November 2024, 09:11:58 CET schrieb Roger Price: What about juste enter blkid as root? Will also give UUID and Label. Best Hans > Sorry, the formatting was messed up and the message unreadable. > > On Tue, 26 Nov 2024, George at Clug wrote: > > "$ lsblk -f" output is very nice ! Thanks. > > I tried this and noticed UUID duplication in the output. I attach a small > text file which shows what I saw. UUID sdg6 = UUID sdh6 ! > > NAME FSTYPE UUID > ... > ├─sdg6 linux_raid_membe3 f5e37a29-357a-e3f2-c731-e29eddce5e > │ └─md3 ext4 1.039c24711-ab43-497c-bf3e-12b4032575a.4G > ... > ├─sdh6 linux_raid_membe3 f5e37a29-357a-e3f2-c731-e29eddce5e91 > │ └─md3 ext4 39c39c24711-ab43-497c-bf3e-12b403257.4G > > If I wanted to retire /dev/sdg6 from the Raid array, I would not be able to > use the UUID, only the unique SDxn. > > Aren't UUIDs supposed to be unique? Roger
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| From | Roger Price <debian@rogerprice.org> |
|---|---|
| Date | 2024-11-26 10:10 +0100 |
| Message-ID | <JMZK1-bITN-3@gated-at.bofh.it> |
| In reply to | #274889 |
On Tue, 26 Nov 2024, Hans wrote:
> What about juste enter blkid as root?
> Will also give UUID and Label.
# blkid /dev/sdg6
/dev/sdg6: UUID="f5e37a29-357a-e3f2-c731-e29eddce5e91"
UUID_SUB="8ae02b9d-d818-1d8a-88f6-5cb77b15d0eb"
LABEL="10.218.0.100:3" TYPE="linux_raid_member" PARTUUID="000871f1-06"
# blkid /dev/sdh6
/dev/sdh6: UUID="f5e37a29-357a-e3f2-c731-e29eddce5e91"
UUID_SUB="7821cc06-e7f5-358b-cf95-fb0ec2f34585"
LABEL="10.218.0.100:3" TYPE="linux_raid_member" PARTUUID="0000b24f-06"
# blkid /dev/md0
/dev/md0: UUID="8a31b513-cd62-4639-b5e5-3a8f8879164f" BLOCK_SIZE="4096"
TYPE="ext4"
The UUIDs are the same for sdg6 and sdh6 but there is a UUID_SUB to distinguish
them. blkid sees a new value for md0's UUID, not the same as lsblk.
Roger
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| From | George at Clug <Clug@goproject.info> |
|---|---|
| Date | 2024-11-26 10:40 +0100 |
| Message-ID | <JN0d4-bJ4z-7@gated-at.bofh.it> |
| In reply to | #274892 |
On Tuesday, 26-11-2024 at 20:08 Roger Price wrote: > On Tue, 26 Nov 2024, Hans wrote: > > > What about juste enter blkid as root? > > Will also give UUID and Label. > > # blkid /dev/sdg6 > /dev/sdg6: UUID="f5e37a29-357a-e3f2-c731-e29eddce5e91" > UUID_SUB="8ae02b9d-d818-1d8a-88f6-5cb77b15d0eb" > LABEL="10.218.0.100:3" TYPE="linux_raid_member" PARTUUID="000871f1-06" > > # blkid /dev/sdh6 > /dev/sdh6: UUID="f5e37a29-357a-e3f2-c731-e29eddce5e91" > UUID_SUB="7821cc06-e7f5-358b-cf95-fb0ec2f34585" > LABEL="10.218.0.100:3" TYPE="linux_raid_member" PARTUUID="0000b24f-06" > > # blkid /dev/md0 > /dev/md0: UUID="8a31b513-cd62-4639-b5e5-3a8f8879164f" BLOCK_SIZE="4096" > TYPE="ext4" > > The UUIDs are the same for sdg6 and sdh6 but there is a UUID_SUB to distinguish > them. blkid sees a new value for md0's UUID, not the same as lsblk. Thanks for the clarification, Roger. This is important to understand if working with RAID. What does /etc/fstab have, I wonder? RAID, like LVM, to me is a type of virtualisation of storage, hence is not exactly the same as a physical disk drive or partition on the disk drive. I am guessing UUID is for the OS to see the visualised (RAID) storage, where as UUID_SUB is for the actual partition on the physical disk? Today I learned a bit more about /dev/disk, but that left me realising there is much more to learn. I really don't know what to think of all of these folders. # ls -hal /dev/disk/ # ls -hal /dev/disk/by-id # ls -hal /dev/disk/by-uuid But the following worked well for me when putting a boot ISO to a USB memory stick. # cp [isoimagefile.iso] /dev/disk/by-id/usb-SMI_USB_DISK-0:0 # sync The world is full of mysteries for those too lazy to do heaps of reading and research. George. > > Roger > >
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| From | Andy Smith <andy@strugglers.net> |
|---|---|
| Date | 2024-11-26 16:30 +0100 |
| Message-ID | <JN5FM-bMw7-7@gated-at.bofh.it> |
| In reply to | #274883 |
Hi, On Tue, Nov 26, 2024 at 09:11:58AM +0100, Roger Price wrote: > On Tue, 26 Nov 2024, George at Clug wrote: > > > "$ lsblk -f" output is very nice ! Thanks. > > I tried this and noticed UUID duplication in the output. I attach a small > text file which shows what I saw. UUID sdg6 = UUID sdh6 ! > > NAME FSTYPE UUID > ... > ├─sdg6 linux_raid_membe3 f5e37a29-357a-e3f2-c731-e29eddce5e > │ └─md3 ext4 1.039c24711-ab43-497c-bf3e-12b4032575a.4G > ... > ├─sdh6 linux_raid_membe3 f5e37a29-357a-e3f2-c731-e29eddce5e91 > │ └─md3 ext4 39c39c24711-ab43-497c-bf3e-12b403257.4G > > If I wanted to retire /dev/sdg6 from the Raid array, I would not be able to > use the UUID, only the unique SDxn. > > Aren't UUIDs supposed to be unique? People see the phrase "UUID" and think every UUID is the same. Your computer has lots of different UUIDs. What you see above is the mdadm array UUID. It is meant to be unique PER ARRAY (on that system). Those devices are part of the same array thus they have the same ARRAY UUID. You don't have a filesystem on /dev/sdg6 or /dev/sdh6. If you did then it would have a FILESYSTEM UUID. If you want to refer to sdg6 or sdh6 without using /dev/sd* then you can use any of the /dev/disk/by-* paths for them. See also the output of "mdadm --examine /dev/sdg6" and "mdadm --detail /dev/md3". Thanks, Andy -- https://bitfolk.com/ -- No-nonsense VPS hosting
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