4

I have been looking into making backups of personal files that can be put in a closet and forgotten about for years without worrying about disk failure or bit rot, and it seems that HTL BD-R's are the way to go.

I have a folder that contains files that I would like to back up. Every once in a while, some of these files may get updated or new files may be added, and I would like those to be backed up. But BD-R's are write-once media.

If I understand correctly, the UDF filesystem supports writing modifications and new files on write-once media using Virtual Allocation Tables. Since UDF seems pretty well supported across operating systems, I would like to take advantage of this for this particular usecase.

On Linux, I attempted to simulate a format a BD-R as UDF using the following command:

$ mkudffs -l Test -m bdr -n --vat /dev/sr0
Note: Not writing to device, just simulating
filename=/dev/sr0
label=Test
uuid=66f5a2c157e54521
blocksize=2048
blocks=1
udfrev=2.50
mkudffs: Error: Not enough blocks on device

First I was surprised to see that it complained about not having enough blocks. So I decided to remove the -n (simulate) parameter and just see what happens:

$ mkudffs -l NewHouse -m bdr --vat /dev/sr0
mkudffs: Error: Cannot open device '/dev/sr0': Read-only file system

At this point, I'm not sure what I'm doing wrong. Any pointers? And is my understanding of UDF with regards to write-once media correct? And in general, is this approach a good idea? Would a BD-RE make more sense here?

9a3eedi
  • 508

1 Answers1

2

It turns out that BD-R's can only be formatted with UDF 2.5 or greater, if I understand correctly from Wikipedia.

Linux unfortunately does not support writing to UDF 2.5 filesystems as of kernel version 6.11, although it can read from them. The maximum it supports right now is writing to UDF 2.01, and reading from 2.6 (latest). UDFTools depends on the kernel to do its writing, so this means you won't be able to format it on Linux.

My current workaround is to use Windows and set the BD-R as a "Live Filesystem", which formats it with UDF 2.6, and allows you to write, overwrite, and delete files on it (without reclaiming space, of course). The Bluray would still be readable on Linux, at least, because UDF 2.6 is read-only compatible with UDF 2.5, which Linux supports.

9a3eedi
  • 508