Comment 18 for bug 1780332

asi,

I would rule out the lack of rules because on both xenial and bionic we have LVM udev rules with the following line that is supposed to create a LUKS UUID-based symlink:`

ENV{ID_FS_USAGE}=="filesystem|other|crypto", ENV{ID_FS_UUID_ENC}=="?*", SYMLINK+="disk/by-uuid/$env{ID_FS_UUID_ENC}"

https://git.launchpad.net/~usd-import-team/ubuntu/+source/lvm2/tree/udev/13-dm-disk.rules.in?h=ubuntu/xenial
https://git.launchpad.net/~usd-import-team/ubuntu/+source/lvm2/tree/udev/13-dm-disk.rules.in?h=ubuntu/bionic

The above test have shown that the symlink gets created on bionic.

For xenial it seems to be the same but this test is different in terms of CPU load present on a machine (there is no load in my tests now in comparison to the situations based on which we filed this bug):

uname -a
Linux maas-vhost6 4.4.0-135-generic #161-Ubuntu SMP Mon Aug 27 10:45:01 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

grep -RP ID_FS_UUID_ENC /lib/udev/rules.d/
/lib/udev/rules.d/60-persistent-storage-dm.rules:ENV{ID_FS_USAGE}=="filesystem|other|crypto", ENV{ID_FS_UUID_ENC}=="?*", SYMLINK+="disk/by-uuid/$env{ID_FS_UUID_ENC}"
/lib/udev/rules.d/60-persistent-storage.rules:ENV{ID_FS_USAGE}=="filesystem|other|crypto", ENV{ID_FS_UUID_ENC}=="?*", SYMLINK+="disk/by-uuid/$env{ID_FS_UUID_ENC}"
/lib/udev/rules.d/69-bcache.rules:ENV{ID_FS_UUID_ENC}=="?*", SYMLINK+="disk/by-uuid/$env{ID_FS_UUID_ENC}"
/lib/udev/rules.d/69-lvm-metad.rules:ENV{ID_FS_UUID_ENC}=="?*", SYMLINK+="disk/by-id/lvm-pv-uuid-$env{ID_FS_UUID_ENC}"
/lib/udev/rules.d/63-md-raid-arrays.rules:ENV{ID_FS_USAGE}=="filesystem|other|crypto", ENV{ID_FS_UUID_ENC}=="?*", SYMLINK+="disk/by-uuid/$env{ID_FS_UUID_ENC}"

lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 64G 0 disk
`-sda1 8:1 0 64G 0 part /
sdb 8:16 0 8G 0 disk
sdc 8:32 0 102.4M 0 disk
sdd 8:48 0 102.4M 0 disk
sde 8:64 0 102.4M 0 disk
vda 253:0 0 102.4M 0 disk
vdb 253:16 0 102.4M 0 disk
nvme0n1 259:0 0 20G 0 disk
nvme1n1 259:1 0 20G 0 disk

tree /dev/disk/by-uuid/
/dev/disk/by-uuid/
└── d26a75c9-15f7-41de-8c0e-20f795ed5729 -> ../../sda1

0 directories, 1 file

sudo cryptsetup luksFormat /dev/sdb

WARNING!
========
This will overwrite data on /dev/sdb irrevocably.

Are you sure? (Type uppercase yes): YES
Enter passphrase:
Verify passphrase:

ubuntu@maas-vhost6:~$ tree /dev/disk/by-uuid/
/dev/disk/by-uuid/
├── 42bf3808-9987-454f-be27-5d6c9b9c5c12 -> ../../sdb
└── d26a75c9-15f7-41de-8c0e-20f795ed5729 -> ../../sda1

0 directories, 2 files

sudo cryptsetup luksDump /dev/sdb | grep UUID
UUID: 42bf3808-9987-454f-be27-5d6c9b9c5c12