247 lines
11 KiB
Plaintext
247 lines
11 KiB
Plaintext
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'''Libburnia Frequently Asked Questions'''
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Please post your questions to
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[http://mailman-mail1.webfaction.com/listinfo/libburn-hackers/ libburn-hackers mailing list].
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----------------------------------------------------------------------------
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'''Content:'''
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----------------------------------------------------------------------------
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Burning:
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[#diff_cdrskin_xorriso What is the difference between cdrskin and xorriso ?]
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Imaging:
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[#edit_files Is there a way to edit files inside the ISO image ?]
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[#boot_arch For which architectures xorriso is able to create bootable images ?]
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[#isohybrid How to enable booting from USB stick ?]
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[#partition_offset What is partition offset feature all about?]
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[#partition_offset_apple Partition offset bad on Apple ?]
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Development:
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[#api_specs Where are the APIs of libburnia libraries described ?]
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[#gui_advise I want to write a GUI on the top of libburnia libraries. Any pointers or recommendations ?]
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Miscellaneous:
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[#example_links Where to see examples ?]
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[#xorriso_aliases What personalities are supported by xorriso ?]
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[#xorriso_dialog_mode What is xorriso dialog mode useful for ?]
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[#version_numbers Why is every second release missing ?]
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----------------------------------------------------------------------------
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'''Burning'''
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----------------------------------------------------------------------------
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===== What is the difference between cdrskin and xorriso ? ===== #diff_cdrskin_xorriso
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[wiki:Cdrskin cdrskin] is a dedicated emulator of program cdrecord, based on
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libburn. It tries to be as similar to cdrecord as is possible under that
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premise.
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[wiki:Xorriso xorriso] is an integrated tool which creates, loads, manipulates,
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and writes ISO 9660 filesystem images with Rock Ridge extensions.
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It is based on libburn, libisofs, and libisoburn. One of its features is
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the emulation of the corresponding tasks as done by mkisofs and cdrecord.
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----------------------------------------------------------------------------
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'''Imaging'''
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----------------------------------------------------------------------------
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===== Is there a way to edit files inside the ISO image ? ===== #edit_files
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File content cannot be altered. But files may be replaced by new copies from
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the disk filesystem.
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The main method of manipulating an existing ISO image is to append a session
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with a new complete directory tree and the file content of the added or
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overwritten files. Depending on the media type you get gaps between sessions
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of up to 20 MB. So better try to do all foreseeable changes by one add-on
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session.
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===== For which architectures xorriso is able to create bootable images ? ===== #boot_arch
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Currently it supports systems with PC-BIOS via El Torito for booting from
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CD, DVD, or BD media, and via MBR for booting from memory sticks or hard
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disks. Further it supports machines with MIPS processor from SGI (Big Endian)
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and DEC (Little Endian), and SUN SPARC machines.
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(See [http://bazaar.launchpad.net/%7Elibburnia-team/libisofs/scdbackup/annotate/head%3A/doc/boot_sectors.txt libisofs/doc/boot_sectors.txt]
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for technical details.)
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Machines which support EFI may either boot via El Torito or use the files
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of the ISO image directly. It is possible to append to the ISO image a
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writeable FAT12 partition where files for EFI may be stored and changed.
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===== How to enable booting from USB stick ? ===== #isohybrid
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The ISOLINUX boot loader is normally started from CD, DVD or BD media
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by a PC-BIOS via an El Torito boot record. But if the ISO image resides on an
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USB stick or another hard-disk-like device, then PC-BIOS ignores El Torito
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and rather expects a Master Boot Record (MBR). Both boot record types can
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reside in the same ISO image. Therefore it is possible to create an MBR that
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starts the boot image file of ISOLINUX which is already target of the El Torito
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boot record. This kind of MBR is called "isohybrid". ISOLINUX provides
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a program named isohybrid to patch existing images, but libisofs can create an
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MBR already when producing the ISO image. See in
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[http://www.gnu.org/software/xorriso/man_1_xorriso.html manual page of xorriso]
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option -boot_image with arguments "isolinux" "system_area=",
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and -as mkisofs option -isohybrid-mbr.
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See [http://en.wikipedia.org/wiki/Master_boot_record Wikipedia on MBR] for
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general information about PC-DOS Master Boot Records, and
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[http://syslinux.zytor.com/wiki/index.php/ISOLINUX ISOLINUX wiki] for special
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information about ISOLINUX. The wiki example with mkisofs can be performed
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as well by help of xorriso option -as mkisofs.
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A similar combination of El Torito and MBR is created by GRUB2 tool
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grub-mkrescue. See [http://www.gnu.org/software/grub/ homepage of GNU GRUB 2]
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for general information.
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===== What is partition offset feature all about? ===== #partition_offset
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If an MBR is present, then it contains a partition table with up to four
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entries. The MBR is located at the very start of the ISO image. By
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tradition the first partition should begin only after the range of MBR and
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eventual supporting data blocks. On hard disk one often sees partition 1
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starting at byte 63*512. Further it is tradition that the payload filesystem
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is mountable via one of the partitions.
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The isohybrid MBR has its only partition start at byte 0. Thus it is mountable
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but does not obey the tradition to begin only after the MBR. The grub-mkrescue
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MBR on the other hand has partition 1 start at byte 512, which makes it
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unmountable. Only the unpartitioned base device can be mounted. (On GNU/Linux
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e.g. /dev/sdb is the base device whereas /dev/sdb1 is partition 1.)
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The compromise offered by libisofs is to create a second superblock at
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address 16*2048 and to let start partition 1 at this address. The second
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superblock leads to a second directory tree which takes into account the
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address difference between partition 1 and the base device. So the image
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gets mountable via both devices and reserves 32 kB for boot manager software
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where it may manipulate and augment the MBR.
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(See [http://libburnia-project.org/wiki/PartitionOffset Partition Offset Wiki]
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for examples.)
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There are reports of machines which will not boot from USB stick if
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partition offset is 0.
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===== Partition offset bad on Apple ? ===== #partition_offset_apple
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Apple's "Snow Leopard" operating system refuses to mount Debian CD images
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with non-zero partition offset.
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The issue is still under investigation. But for now one has to choose
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between mountability on Apple "Snow Leopard" or bootability from USB stick
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on Kontron CG2100 "carrier grade server".
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----------------------------------------------------------------------------
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'''Developing'''
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----------------------------------------------------------------------------
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===== Where are the APIs of libburnia libraries described ? ===== #api_specs
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The decisive references are the inclusion headers of the libraries
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<libburn/libburn.h>, <libisofs/libisofs.h>, <libisoburn/libisoburn.h>,
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and <libisoburn/xorriso.h>.
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Current SVN versions of these files:
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[http://libburnia-project.org/browser/libburn/trunk/libburn/libburn.h libburn/libburn.h] ,
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[http://bazaar.launchpad.net/%7Elibburnia-team/libisofs/scdbackup/annotate/head%3A/libisofs/libisofs.h libisofs/libisofs.h] ,
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[http://libburnia-project.org/browser/libisoburn/trunk/libisoburn/libisoburn.h libisoburn/libisoburn.h] ,
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[http://libburnia-project.org/browser/libisoburn/trunk/xorriso/xorriso.h libisoburn/xorriso.h]
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Doxygen generated API descriptions at
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[http://api.libburnia-project.org api.libburnia-project.org]
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might be slightly behind the latest developments.
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===== I want to write a GUI on the top of libburnia libraries. Any pointers or recommendations ? ===== #gui_advise
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Most appreciated would be a GUI for xorriso which allows to copy files from
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a view of the hard disk filesystem to a view of the ISO filesystem, and vice
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versa. The xorriso implementation is located inside libisoburn.
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Each option that is described in
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[http://www.gnu.org/software/xorriso/man_1_xorriso.html man 1 xorriso]
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can be performed by a corresponding C function that is defined in
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[http://libburnia-project.org/browser/libisoburn/trunk/xorriso/xorriso.h xorriso.h].
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Further there are calls for library startup and shutdown, for problem
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handling, and for the interpreters of xorriso's command line interface.
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The xorriso API encapsulates calls to libisofs, libburn, and libisoburn.
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An alternative to the xorriso C API is xorriso dialog mode.
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[#xorriso_dialog_mode See below.]
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The known existing GUIs [http://www.xfce.org/projects/xfburn/ Xfburn],
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[http://projects.gnome.org/brasero/ Brasero],
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[http://flburn.sourceforge.net/ FlBurn]
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rather use libisofs and libburn directly.
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(Please submit an URI if you want your libburnia GUI application mentioned
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here.)
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----------------------------------------------------------------------------
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'''Miscellaneous'''
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----------------------------------------------------------------------------
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===== Where to see examples ? ===== #example_links
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[http://www.gnu.org/software/xorriso/man_1_xorriso.html#EXAMPLES xorriso examples] ,
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[http://scdbackup.sourceforge.net/man_1_cdrskin_devel.html#EXAMPLES cdrskin examples] ,
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[http://libburnia-project.org/browser/libburn/trunk/test/libburner.c libburner.c a minimal but complete burn program]
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(also illustrated at the end of [http://api.libburnia-project.org/libburn/ libburn API intro]).
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===== What personalities are supported by xorriso ? ===== #xorriso_aliases
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The name by which xorriso is started may trigger certain features which
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normally would need to be enabled by program options.
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xorrisofs starts up in mkisofs emulation mode, which otherwise would have to
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be entered by command -as "mkisofs".
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xorrecord starts up in cdrecord emulation mode, which is normally entered by
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command -as "cdrecord". This emulation is only able to write a single data
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track as new session to blank or appendable media. No audio. No multiple
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tracks in one session.
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osirrox allows to copy files from ISO image to disk and to apply option -mount
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to one or more of the existing ISO sessions. This is normally enabled by
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option -osirrox "on:o_excl_off".
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===== What is xorriso dialog mode useful for ? ===== #xorriso_dialog_mode
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Dialog mode is initiated if -dialog "on" is among the program arguments.
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It can be used to inspect and exploit existing ISO 9660 images or
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to explore xorriso's behavior in order to develop the command sequence
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for a batch run.
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Frontend programmers may fork xorriso initiating a xorriso dialog session
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(-dialog "on" -use_readline "off" -pkt_output "on" -mark "done"),
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and interact with it from their own program via pipes connected to
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xorriso's stdin and stdout. This is more efficient than forking xorriso
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every now and then to perform various commands in order to complete
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complex tasks like image size prediction.
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===== Why is every second release missing ? ===== #version_numbers
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Releases have an even third version number. Like 0.5.6 or 1.0.4.
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During development the next higher odd number is used. E.g. 0.5.7 or 1.0.5.
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The content of release tarballs does not get changed without changing
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their name. The development tarballs of xorriso and cdrskin may change
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their content without notice.
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----------------------------------------------------------------------------
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Site maintainer: Do not edit this wiki directly but rather the SVN version
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of libisoburn/trunk/doc/faq.wiki. When done, paste it into the wiki editor.
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