On Thursday, 19 March 2020 19:08:55 GMT n952162 wrote: > On 2020-03-19 19:43, Michael wrote: > > On Thursday, 19 March 2020 18:32:12 GMT n952162 wrote: > >> On 2020-03-19 19:04, Michael wrote: > >>> On Thursday, 19 March 2020 17:03:15 GMT Ian Zimmerman wrote: > >>>> On 2020-03-19 10:59, n952162 wrote: > >>>>> I changed the UUID of all the partitions of the second drive and now > >>>>> all my devices are linked to in /dev/disk/by-uuid. I still have > >>>>> no/dev/disk/by-label, though. Also, my swap file on a mounted drive > >>>>> wasn't mounted, which was my original problem ;-( > >>>> > >>>> Do they in fact have labels? Just checking. > >>>> > >>>> Also, you're not not clear if your _partition_ still isn't getting > >>>> mounted, or just the swap file not getting activated. > >>>> > >>>> For a problem like this, there _has_ to be something in the log. > >>> > >>> We're using the term 'partition' here, but to avoid confusion, we have > >>> GPT > >>> partition table UUIDs (PARTUUID) and we have filesystem UUIDs (UUID). > >>> > >>> Similarly, we also have filesystem labels and GPT partition labels. > >>> > >>> Therefore it helps if there is consistency in the IDs being used to > >>> mount > >>> partitions. > >> > >> I used the UUID column of blkid(8) on the fstab entry, with UUID=. If > >> that is the partition UUID, where, how, and wherefore are filesystem > >> UUIDs? > > > > lsblk -o +PARTUUID,UUID > > > > will show both, but blkid also print filesystem UUID and partition table > > PARTUUID. > > Okay, then I got it backwards: both blkid(8)'s UUID and /etc/fstab's > UUID are the filesystem UUID. What is the partition UUID used for?
GPT partition tables also have a 'UUID' for each partition, which is stored in the GPT tables. The GUID Partition Table (GPT) is called so because every partition on a disk has a “globally unique identifier,” or GUID (aka. PARTUUID). GPT tables use 64-bit sector pointers for each partition, but I don't know if the 128-bit code of GUID/PARTUUID contains info on the start sector of a GPT partition. Anyway, you can specify block devices to be mounted in your /etc/fstab using various methods. 1. The good ol' file name of a block device: /dev/sdaX However, if you swap drives around, don't be surprised if your drive has been renamed/renumbered. The /dev/sdaX device file name will now point to a different disk/partition. 2. Partition UUID: PARTUUID=xxxxxxx-xxxxxxx-xxx-xxx This is permanent and won't change when you swap disks around, unless you repartition your disk. You need a GPT table type for this method. 3. Filesystem UUID: UUID=xxxxxx-xxxxxxx-xxx-xxxxxxxxx This is permanent and will also not change, unless you reformat your filesystem. 4. Filesystem LABEL: LABEL=MySWAP This won't change unless you reformat the filesystem, or change its LABEL. 5. Partition PARTLABEL: PARTLABEL=SWAP1 This won't change unless you repartition the disk, or change its PARTLABEL. Finally, I don't think you can use the hardware specific ID, found under /dev/ disk/by-id/wwn-xxxxxxxxxxxxxxxxxx-part1, which is a symlink to the /dev/sda1 name.
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