sdb2 is ext3 fs on a 16G flash stick, very typical kind, made with fdisk

when i use "tune2fs -U foo /dev/sdb2" it says nothing, light flashes. after that, dumpe2fs says UUID is <none>

history: I want to use UUID= in my /etc/fstab because VirtualBox doesn't support disk LABELsetting or /dev/sdb2 setting. i'm using .vmdk which means the image is a softlink (per say) to a real device. VirtualBox assigns same UUID to all .vmdk, then one has to set the "right / different" UUID i guess if one expects to boot using the same UUID as real (also vb refuses to add 2nd disk unless UUID is changed in one). Perhaps the VIrtualBox UUID and UUID scored on the device don't have to match, of that i'm unsure it's not documented to such an extent i can learn - i think.

I'm struggling to understand what sort of setup you have here, to be honest, and where VirtualBox fits into it. However, for the tune2fs -U command, could you try:

and see if that sticks. If it does, your -U parameter may not be a valid UUID string.

thank you. but tune2fs doesn't allow "non-standard" numbers: it complains immediately and exits.

for example, given the hex code: 1-1-1-1-1, tune2fs won't even backfill zeros ! (it's doesn't even get fscanf() treatment of numbers)

(00000001-0001-0001-0001-000000000001)

i used a simple uuid, yes. but it passed as a uuid. as far as beign unique within the universe i don't care. it's just for a home lan and because PC are so "unattached" i need a ID i can remember off the top of my head.

virtualbox doesn't use or support LABEL, so i'm stuck using UUID

I'm told UUID is a 128 bit number represented as HEX. Perhaps that's not true. Perhaps if UUID isn't what tune2fs's internal "picker" would choose, then it refuses to write to disk? (if so, that's a security problem, not that i care)

Which version of tune2fs are you using? It should accept the -U random keyword as I suggested, as well as clear and time. Check man tune2fs.

your right, -U random is required, entering in the right format doesn't work

i know hex backwards and forwards. or the manpage is wrong (it says to use alnum hex format with hyphens).

because it was released continually without fixing and the problem is "SO OBVIOUS" i assume it's intentionally broken.

to make this more fun: virtualbox requires uuid of virtual disk template be exactly same as uuid "stored in the real disk", to let you know

Ok, so if you won't take my advice on trying -U random, please try setting any other superblock value with tune2fs, e.g. -c max-mount-counts, and see if it sticks.

I don't think a UUID you can remember off the top of your head is a worthwhile goal here. Maybe you could just type out a valid UUID to assign to the drive, and then make an alias that echos that UUID to the terminal so you don't need to remember the whole thing.