[Pkg-libburnia-devel] Bug#1010098: xorriso: please allow -cut-out directly from block devices

[Ivan Shmakov]

Package: xorriso
Version: 1.5.0-1
Severity: wishlist
Control: found -1 1.5.2-1

	[Please do not Cc: me, for I’m “on the list,” so to say, and
	I try to reserve my inbox for private communication only.
	I’d have set up Mail-Followup-To:, but there doesn’t seem to
	be a way to make it point to the report being filed.]

	I’m filing this bug against versions from oldstable and
	stable, for that’s so far the only Debian packages’ versions
	I’ve tested for this issue.  Regardless, given that the
	behavior is the same for a recent Git revision, and that
	there doesn’t seem to be any relevant Debian-specific
	patches under [1], it stands to reason that the requested
	feature is not available in Debian testing and Sid, either.

[1] http://sources.debian.org/src/libisoburn/1.5.4-2/debian/patches/

	It would be handy to be able to use xorriso(1) to backup
	(portions) of block devices to optical media; yet it doesn’t
	seem to be supported.  E. g., on Buster:

bash$ xorriso -dev stdio:/tmp/cd"$RANDOM".image -follow link \
          -cut-out /dev/vgjubca-bk-i/lvepeci-x626512db 37M 13M lvxxx_37m+13m \
          -find / -exec lsdl -- -commit 
xorriso 1.5.0 : RockRidge filesystem manipulator, libburnia project.

Drive current: -dev 'stdio:/tmp/cd4973.image'
Media current: stdio file, overwriteable
Media status : is blank
Media summary: 0 sessions, 0 data blocks, 0 data,  XXXm free
xorriso : FAILURE : -cut_out: Unsupported file type (block_device) with '/dev/vgjubca-bk-i/lvepeci-x626512db' : No such file or directory
xorriso : aborting : -abort_on 'FAILURE' encountered 'FAILURE'
bash$ 

	On Bullseye:

bash$ xorriso -dev stdio:/tmp/cd"$RANDOM".image -follow link \
          -cut-out /dev/vgjubca-bk-i/lvepeci-x626512db 37M 13M lvxxx_37m+13m \
          -find / -exec lsdl -- -commit 
xorriso 1.5.2 : RockRidge filesystem manipulator, libburnia project.

Drive current: -dev 'stdio:/tmp/cd1415.image'
Media current: stdio file, overwriteable
Media status : is blank
Media summary: 0 sessions, 0 data blocks, 0 data,  XXXm free
xorriso : FAILURE : -cut_out: Unsupported file type (block_device) with '/dev/vgjubca-bk-i/lvepeci-x626512db' : No such file or directory
xorriso : aborting : -abort_on 'FAILURE' encountered 'FAILURE'
bash$ 

	The problem is due to /both/ libisoburn (to a lesser degree)
	and libisofs relying on struct stat .st_size field (and the
	respective S_ISREG check.)

	I’ve made a very crude patch (MIMEd) that replaces the
	st_size checks for non-regular files with checks against the
	size reported by lseek (, 0, SEEK_END), if available; and in
	some cases forgoes the check for non-regular files altogether.

	Consider, e. g.:

bash$ xorriso -dev stdio:/tmp/cd"$RANDOM".image -follow link \
          -cut-out /dev/vgjubca-bk-i/lvepeci-x626512db 37M 13M lvxxx_37m+13m -find / -exec lsdl -- -commit 
xorriso 1.5.5 : RockRidge filesystem manipulator, libburnia project.

Drive current: -dev 'stdio:/tmp/cd14597.image'
Media current: stdio file, overwriteable
Media status : is blank
Media summary: 0 sessions, 0 data blocks, 0 data,  XXXm free
drwxr-xr-x    1 0        0               0 Apr 24 10:16 '/'
-rw-rw----    1 0        6        13631488 Apr 10 10:58 '/lvxxx_37m+13m'
xorriso : UPDATE : Writing:       3985s   58.2%   fifo   0%  buf  50%
ISO image produced: 6679 sectors
Written to medium : 6848 sectors at LBA 32
Writing to 'stdio:/tmp/cd14597.image' completed successfully.

xorriso : NOTE : Re-assessing -outdev 'stdio:/tmp/cd14597.image'
xorriso : NOTE : Loading ISO image tree from LBA 0
xorriso : UPDATE :       1 nodes read in 1 seconds
Drive current: -dev 'stdio:/tmp/cd14597.image'
Media current: stdio file, overwriteable
Media status : is written , is appendable
Media summary: 1 session, 6679 data blocks, 13.0m data,  XXXm free
Volume id    : 'ISOIMAGE'
bash$ 

	Checking if the intended data was indeed written to the image
	with icat(1):

bash$ /usr/bin/time -- cmp -n 13M -i 37M:0 -- \
          /dev/vgjubca-bk-i/lvepeci-x626512db \
          <(icat /tmp/cd14597.image 1) 
0.01user 0.04system 0:00.18elapsed 29%CPU (0avgtext+0avgdata 1088maxresident)k
27112inputs+0outputs (0major+95minor)pagefaults 0swaps
bash$ 

-- 
FSF associate member #7257  http://am-1.org/~ivan/
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