Hallo, Hugo, Du meintest am 03.01.13: [...] >>> Trying to use filesystem labels to give unique and stable device >>> IDs is the wrong tool for the job. >> I beg to differ. On my machines it's the simpliest way, and it's a >> sure way. > No, because *it* *doesn't* *work*. This is not a bug. This is how > things have always behaved -- you're relying on an assumption (one FS > per device) which simply isn't true any longer. No - I don't rely on such an assumption. In the special case I'm just working with I want to use the whole disk only for btrfs. In other cases I work with partitions, and there is just the same problem: at least "blkid" and "findfs" don't work when more than 1 device has the same label (p.e. /dev/sda3 and /dev/sdc5). >> And how is the way for a system which doesn't use "udev"? > There isn't one ready-made. Your options are: > * run udev > * write something which uses (e.g.) SMART information on block > devices to extract a unique ID, and convert that into a stable > device label (which is effectively what udev does) Sorry - I don't need the "unique ID" for the machines. I can use (p.e.) e2label /dev/sda3 Var for labelling an ext2/3/4 partition. Works like a charm, especially for USB disks. > * find some piece of the device which isn't going to be overwritten > by partition tables, GPTs, filesystems, or other kinds of > metadata, and write your label into there; again, you will need to > develop your own tool for reading/writing this information Sorry - that's not necessary. When I connect the disk then I can search with "findfs" without having mounted any partition. >> Labelling via "btrfs filesystem label <device> <label>" works well. > Clearly it doesn't, because you're having problems with it. No - not at all! I've only problems when I use the "-L" option of "mkfs.btrfs" together with more than 1 device in the "mkfs.btrfs" command. > The > behaviour where only one device in the FS gets the label, immediately > after a btrfs label command, is a bug -- *all* of the devices in the > FS should get the label. You're trying to rely on the behaviour of a > bug, not on the designed behaviour of the system. What works: Building the filesystem with "mkfs.btrfs", without the "-L" option Then (p.e.) btrfs filesystem label <device> <label> (unmounted system) Then I can check the existence (not only for btrfs formatted disks) with findfs LABEL=<label> && mount LABEL=<label> <mountpoint> As mentioned: works not only with btrfs, works fine especially for USB disks. I don't need any UUID etc. for this way of identyfying. I don't need to change the mount directive when I change a smaller disk to a bigger disk. Viele Gruesse! Helmut -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html