From: "Thomas Schmitt" <scdbackup@gmx.net>
Date: Mon, 24 Mar 2025 08:48:34 +0100

You could use command -rollback_end to refrain from writing:

xorriso ...the.desired.commands... -rollback_end

This will perform the commands but then just end the program run
instead of writing the result and thus reading all the content of
the files which were mapped into the ISO.

Thomas, have you tested that?

Sessions 52 and 53, listed below, were created with these commands.

# dest=/dev/sdd
# xorriso -for_backup \
-dev stdio:"$dest" \
-assert_volid 'BOB.*' fatal \
-volid BOB."$(date '+%Y.%m.%d.%H:%M:%S')" \
-update_r "$source" / \
-commit \
-toc \
-check_md5 failure -- \
-rollback_end ;

Then check the table of contents.

# xorriso -dev stdio:/dev/sdd -toc | tail -n 4
xorriso 1.5.6 : RockRidge filesystem manipulator, libburnia project.

xorriso : NOTE : Loading ISO image tree from LBA 0
xorriso : UPDATE : 4777 nodes read in 1 seconds
Drive current: -dev 'stdio:/dev/sdd'
Media current: stdio file, overwriteable
Media status : is written , is appendable
Media summary: 53 sessions, 6555341 data blocks, 12.5g data, 453g free
Volume id : 'BOB.2026.02.06.08:57:28'
ISO session : 52 , 6524768 , 501s , BOB.2026.01.30.17:03:02
ISO session : 53 , 6525280 , 30898s , BOB.2026.02.06.08:57:28
Media summary: 53 sessions, 6555341 data blocks, 12.5g data, 453g free
Media nwa : 6556192s
#

For session 52, no changed files to write. Hence 501s for a
directory. For session 53, several files written.

Dry run?

Thx, ... P.

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