Hi,
Tim Woodall wrote:
> If I wrote one session per day that would be c 30 sessions per disc.
This should be doable on any BD-R capable drive.
> I'd also need to find a drive
> where I can verify what has been written without it ejecting the disk
> first (or at least be able to reload the disk automatically).
That's not a matter of the drive but of the Linux kernel which shows
few love towards DVD and BD media. (I have a patch for a new ioctl()
which would simulate newly loading of a disc without the need for
moving the drive tray. But the kernel shows few love for userland
programmers, too.)
But xorriso uses libburn which performs SCSI transactions directly with
the drive (via ioctl SG_IO). So it assesses the medium status on its own
and is able to read freshly written data without drive tray dance.
> I will need to do some experimenting as I don't have any
> experience of writing multi-session disks.
You may practice with a plain data file instead of optical media, by
replacing in the following example the command
-dev /dev/sr0
by e.g.
-dev "$HOME"/xorriso_test.iso
Detailed explanation of the example from man xorriso
"Incremental backup of a few directory trees" :
$ xorriso \
The first command tells xorriso to abort only if there is no hope for any
success. (Default is to abort if a substantial part of the job cannot be
performed.)
-abort_on FATAL \
The following enables recording of MD5 for data files and the whole session,
recording of ACL (getfacl(1)) and of extended file attributes (getfattr(1)).
-for_backup \
By the next command xorriso gets asserted that device numbers of disk
filesystems and the inode numbers of files in the filesystems remain stable
between xorriso runs, unless files get replaced. This assertion speeds up
the comparison of disk filesystem and ISO 9660 filesystem. (Slower would
be comparing the disk files with MD5s of ISO 9660 files, or comparing the
files directly by reading both contents.)
-disk_dev_ino on \
The next command makes sure that only blank media or written media with
a matching ISO 9660 volume id (lsblk FSLABEL) are accepted. This shall
keep you from inserting the wrong medium and thus causing an unduely
big new session. If the volume id of a written medium does not match,
then it emits a FATAL event which will abort the xorriso run:
-assert_volid 'PROJECTS_MAIL_*' FATAL \
Next choose the drive. If it already contains an ISO 9660 session it gets
loaded as base of the file tree comparison and as base of the upcomming
new session:
-dev /dev/sr0 \
Choose a volume id which matches above -assert_volid:
-volid PROJECTS_MAIL_"$(date '+%Y_%m_%d_%H%M%S')" \
Exclude files which end by .o or .swp:
-not_leaf '*.o' -not_leaf '*.swp' \
Check for differences between file tree /home/thomas/projects on hard disk
and ISO 9660 file tree /projects on the backup medium. Any file which
changed, appeared or disappeared since the last backup session will be
properly represented in the overall directory tree of the upcomming new
session.
Unchanged files will appear in the new overall tree too. Their data will
not get newly written but rather be represented by data which was already
recorded by a previous session:
-update_r /home/thomas/projects /projects \
Same for another pair of disk and ISO 9660 file trees. You may add as many
such commands as you need to describe your backup. Each of them gets a
pair of paths as parameter:
-update_r /home/thomas/personal_mail /personal_mail \
The next command causes the new session to be written to medium:
-commit \
After writing is complete, print the new medium state including the list of
sessions:
-toc \
Now comes the checkreading by help of the recorded MD5s for superblock,
directory tree, and file data area of the newly written session:
-check_md5 FAILURE -- \
And finally, if the program did not find reason to abort and if the
drive has a tray motor, eject the tray:
-eject all
Recorded ACL and xattr are not repesented by the Linux kernel when the
ISO gets mounted. But xorriso can extract files including those features
by help of its own commands. The man page has an example
"Restore directory trees from a particular ISO session to disk"
$ xorriso -for_backup \
-load volid 'PROJECTS_MAIL_2008_06_19*' \
-indev /dev/sr0 \
-osirrox on:auto_chmod_on \
-chmod u+rwx / -- \
-extract /projects /home/thomas/restored/projects \
-extract /personal_mail /home/thomas/restored/personal_mail \
-rollback_end
Have a nice day :)
Thomas
