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Why arent we using UUIDs in /etc/fstab?

MelvynDrag
MelvynDrag Posts: 20
in LFS201 Class Forum - Discontinued

I learned to always use UUIDs in my /etc/fstab because partition naming is volatile. I've made a cloud machine unbootable by put /dev/sda1 etc in my fstab instead of UUID=....

Has something changed in the recent past? Why are we referring to partitions by their volatile names rather than their UUIDs?

Comments

  • coop
    coop Posts: 917

    Almost all distributions (probably all ) use UUID in /etc/fstab for the reasons you state. However, they are long and error prone to type and for the purposes of the course it is just easier to use actual partition names (from time to time) because in the VMs etc used in the course the disk naming is not volatile. Personally, I often use LABEL=... instead of UUID or /dev/sdaX for the same reason, as it is helpful when using LVM for example.

    Your point is well taken but is consciously avoided from time to time in LFS201.

    A typical UUID might be 6934b738-1e36-429a-89be-8b97eg2f0556. Try t yping that :) Sure you can cut and paste it from one place to another but for some students taking LFS201 that is not as trivial as it sounds.

  • MelvynDrag
    MelvynDrag Posts: 20

    Thanks for the response!

    I always saw LABEL and PARTLABEL in blkid but never knew what to use it for.

    I do see a danger with these though, seems there is no redundancy protection. I made two partitions and called them both "label", then put them in my fstab. Only one was mounted by mount -a

    So using LABEL/PARTLABEL seems much nicer than UUIDs, just make sure you type everything right and dont duplicate right?

    Also as a curiosity - is there a way to set LABEL with fdisk or parted? I could only set PARTLABEL with parted. To set LABEL I had to use e2label. Wish all the partitioning stuff was in one place!

    Thanks again for the response and sorry for the barrage of questions and comments

  • coop
    coop Posts: 917

    yes LABEL can hit conflicts (has happened to me, for example if you have two disks) so you need to be careful. UUID is better but there are situations where you can change the UUID! For example if you reformat a swap partition it can happen.

    For an ext4 partition you can do
    e2lable /dev/sda4 (to see the label)
    e2label /dev/sda4 SOMELABEL to get it

    It is also an option for mkswap. (-L i believe)

    For other filesystems (such as btrfs, or xfs) you'd have to look at the file system documentation.

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