For Linux there is a self-written block device driver, similar to the loop driver. Creates on demand devices /dev/mycc0, /dev/mycc1, etc., looking at some destination devices.
After the reboot, I entered the dracut emergency shell by specifying the kernel parameter rd.break=initqueue
Two devices were created /dev/loop0 and /dev/mycc0. Both look at /dev/sda2.
udevadm info for /dev/mycc0 does not show fields like ID_FS_UUID, ID_FS_TYPE, etc. For /dev/loop0 it shows.
Wherein:
1: udevadm test-builtin blkid /sys/class/block/loop0 and udevadm test-builtin blkid /sys/class/block/mycc0 - the same! There are fields ID_FS_UUID, ID_FS_TYPE, etc. ...
2: stat and blkid for /dev/loop and /dev/mycc0 are the same
3: cmp -b -l /dev/loop0 /dev/mycc0 - no differences found.
An example of what udevadm info outputs:
Executed udevadm info /dev/loop0:
P: /devices/virtual/block/loop0
N: loop0
L:0
E: DEVPATH=/devices/virtual/block/loop0
E: DEVNAME=/dev/loop0
E: DEVTYPE=disk
E: DISKSEQ=4
E: MAJOR=7
E: MINOR=0
E: SUBSYSTEM=block
E: USEC_INITIALIZED=127559842
E: ID_FS_UUID=mvZqUU-Fa0z-F5j3-cEIW-g5XJ-86la-FxNVkH
E: ID_FS_UUID_ENC=mvZqUU-Fa0z-F5j3-cEIW-g5XJ-86la-FxNVkH
E: ID_FS_VERSION=LVM2 001
E: ID_FS_TYPE=LVM2_member
E: ID_FS_USAGE=raid
Executed udevadm info /dev/mycc0:
P: /devices/virtual/block/mycc0
N:mycc0
L:0
E: DEVPATH=/devices/virtual/block/mycc0
E: DEVNAME=/dev/mycc0
E: DEVTYPE=disk
E: DISKSEQ=9
E: MAJOR=252
E: MINOR=0
E: SUBSYSTEM=block
What can be wrong?
P.S.: Both drivers use /dev/sda2 for ease of testing. I don’t do anything for recording, and if I check separately, only loop0 or only mycc0, then the picture is the same.