New in nbdkit: Create an ISO image on the fly

nbdkit is the pluggable Network Block Device server that Eric and I wrote. I have submitted a talk to FOSDEM next February about the many weird and wonderful ways you can use nbdkit as a flexible replacement for loopback mounting.

Anyway, new in nbdkit 1.7.6 you can now create ISO 9660 (CD-ROM) disk images on the fly from a directory:

# nbdkit iso /boot params="-JrT"
# nbd-client -b 512 localhost /dev/nbd0
# file -bsL /dev/nbd0
ISO 9660 CD-ROM filesystem data 'CDROM'
# mount /dev/nbd0 /tmp/mnt
# ls /tmp/mnt
config-4.18.0-0.rc8.git2.1.fc29.x86_64
config-4.19.0-0.rc1.git3.2.fc30.x86_64
config-4.19.0-0.rc6.git0.1.fc30.x86_64
efi
extlinux
grub2
[etc]
# umount /tmp/mnt
# nbd-client -d /dev/nbd0
# killall nbdkit

That ISO wouldn’t actually be bootable, but you could create one (eg. an El Torito ISO) by adding the appropriate extra parameters.

To head off the first question: If you copy files into the directory while nbdkit is running, do they appear in the ISO? Answer: No! This is largely impossible with the way Linux block devices work.