425 lines
18 KiB
Plaintext
425 lines
18 KiB
Plaintext
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### Libburnia Frequently Asked Questions
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Please post your questions to
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[GNU xorriso mailing list](https://lists.gnu.org/mailman/listinfo/bug-xorriso).
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----------------------------------------------------------------------------
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### Content:
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Google favorites:
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[xorriso not found](#xorriso_not_found)
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[xorriso tutorial](#xorriso_tutorial)
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[xorriso create ISO image](#xorriso_create_iso)
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Burning:
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[What is the difference between cdrskin and xorriso ?](#diff_cdrskin_xorriso)
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[What does that SCSI error message mean ?](#scsi_error)
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[Why is simultaneous burning with multiple drives so slow ?](#concurrent_burn)
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Imaging:
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[Is there a way to edit files inside the ISO image ?](#edit_files)
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[For which architectures xorriso is able to create bootable images ?](#boot_arch)
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[How to enable booting from USB stick ?](#isohybrid)
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[What is partition offset feature all about?](#partition_offset)
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[Partition offset bad on Apple ?](#partition_offset_apple)
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Development:
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[Where are the APIs of libburnia libraries described ?](#api_specs)
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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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Miscellaneous:
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[Where to see examples ?](#example_links)
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[What personalities are supported by xorriso ?](#xorriso_aliases)
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[What is xorriso dialog mode useful for ?](#xorriso_dialog_mode)
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[Why is every second release missing ?](#version_numbers)
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------------------------------------------------------------------------
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### Google favorites
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------------------------------------------------------------------------
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##### xorriso not found <A NAME="xorriso_not_found">
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This message is issued by programs which use [xorriso](Xorriso) for
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producing ISO 9660 filesystem images. E.g. by GRUB2's grub-mkrescue.
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Executable xorriso binaries are normally contained in software packages
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named "libisoburn" or "xorriso".
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If your operating system does not offer such a package, then consider
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to get the [GNU xorriso](http://www.gnu.org/software/xorriso#download)
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source tarball. For instructions read in its
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[README file](http://www.gnu.org/software/xorriso/README_xorriso)
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the paragraph "Compilation, First Glimpse, Installation".
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With grub-mkrescue it is possible to use the resulting binary without further
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installation. Just submit its absolute path with option `--xorriso=`. E.g.:
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```
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grub-mkrescue --xorriso=$HOME/xorriso-1.3.8/xorriso/xorriso -o output.iso
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```
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##### xorriso tutorial <A NAME="xorriso_tutorial">
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There is not much more than the
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[man xorriso examples](http://www.gnu.org/software/xorriso/man_1_xorriso.html#EXAMPLES)
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Volunteers are wanted who make a collection of use cases, ask at bug-xorriso
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for xorriso instructions to fulfill the needs, and describe both in a
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user-readable manner.
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Up to then, the GUI demo [xorriso-tcltk](https://dev.lovelyhq.com/libburnia/libisoburn/raw/HEAD/frontend/README-tcltk)
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[(screenshot)](http://www.gnu.org/software/xorriso/xorriso-tcltk-screen.gif)
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may serve as interactive exploration tool. It needs `xorriso` >= 1.2.6, `Tcl`,
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`Tk` >= 8.4, optionally Tcl / Tk package `BWidget`.
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```
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xorriso-tcltk --script_log_file -
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```
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starts the GUI and will log the essential xorriso commands in the start
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terminal. I.e. click on "Scan for drives" and learn that this operation
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is triggered by xorriso command `-devices`.
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Click the rightmost mouse button while being over any of the GUI elements
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in order to get the particular help text for that element.
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Have [man xorriso](http://www.gnu.org/software/xorriso/man_1_xorriso.html)
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ready to learn what the particular commands mean.
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##### xorriso create ISO image <A NAME="xorriso_create_iso">
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```
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xorriso -outdev $HOME/result.iso \
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-map /home/me/sounds /sounds \
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-map /home/me/pictures /pictures
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```
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This points the output to file `$HOME/result.iso`, which should not yet exist.
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Then it maps disk directory `/home/me/sounds` to ISO directory `/sounds`,
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and `/home/me/pictures` to `/pictures`.
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At program end, the ISO image gets produced and the contents of the
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two directory trees gets copied into the ISO.
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If you have experience with program `mkisofs`, you may also use its
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emulation by xorriso:
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```
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xorriso -as mkisofs \
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-o $HOME/result.iso \
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-graft-points \
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/sounds=/home/me/sounds \
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/pictures=/home/me/pictures
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```
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See [man xorriso](http://www.gnu.org/software/xorriso/man_1_xorriso.html)
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for xorriso native commands.
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See [man xorrisofs](http://www.gnu.org/software/xorriso/man_1_xorrisofs.html)
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for its mkisofs emulation.
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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 ? <A NAME="diff_cdrskin_xorriso">
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[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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[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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##### What does that SCSI error message mean ? <A NAME="scsi_error">
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Error messages labled as "SCSI" stem from the drive. They are codes of
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three hexadecimal numbers, like `[3 0C 00]`. The first number gives an overall
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classification of the problem. The other two numbers give the particular
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error description.
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libburn translates known error codes into text messages. They consist of
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two statements: the overall classification and the error description.
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E.g. `[3 0C 00] Medium error. Write error.`
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The classification allows a guess where the problem cause might sit:
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2 `Drive not ready` : This is a well normal drive state and should be handled
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by libburn. If you see this outside of DEBUG messages then it happened
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at an unexpected occasion. Either libburn did its job wrong, or the hardware
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suffers from blackouts. Hardware can be: drive, cable, bus controller.
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Workaround: Check cables. If possible, try the drive at a different
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bus controller.
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3 `Medium error` : This indicates a problem between drive and medium. libburn
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cannot directly cause such an error by any mistake. If drive and medium
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are balancing on the edge of defect, it is possible that optional settings
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can cause or prevent such errors. But in many cases of drive-medium conflicts
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it is mere incident whether a burn run succeeds or not.
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Workaround: Try other media or another drive.
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4 `Drive error` : The drive or the bus controller accuse themselves of
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doing it wrong. As with "Medium error" this might be aggravated or eased by
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optional settings.
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Workaround: Check cables. If possible, try the drive at a different
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bus controller.
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5 `Illegal request` : The drive did not like a command sent by libburn.
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This may be normal. But if you see this outside of DEBUG messages, then
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either the drive does not comply to MMC or libburn does not do its job right.
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Workaround: Submit an error report to
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[GNU xorriso mailing list](https://lists.gnu.org/mailman/listinfo/bug-xorriso).
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B `Command aborted` : Seems to be generated by some bus controllers or
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operating system SCSI drivers. The newest outbreak is said to be due to USB 3
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and drivers which do not prevent power saving.
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Workaround: Plug USB drives to USB 2 sockets or have a recent operating
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system kernel. If this does not help, contact
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[https://lists.gnu.org/mailman/listinfo/bug-xorriso GNU xorriso mailing list]
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and be ready for experiments.
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##### Why is simultaneous burning with multiple drives so slow ? <A NAME="concurrent_burn">
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It is a known regression of Linux since about 2010 that operating more than
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one drive at the same time via SCSI commands shows severe throughput problems.
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See [the wiki page about this problem](ConcurrentLinuxSr) which offers two
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alternative workarounds in userspace, explanantions of the reason,
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and a link to a remedy proposal by courageous kernel modification.
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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 ? <A NAME="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 ? <A NAME="boot_arch">
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Currently it supports systems with PC-BIOS for booting from CD, DVD, or BD
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media, and from memory sticks or hard disks. The same feature range is
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supported for systems with EFI firmware with x86 or ARM processor.
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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 [libisofs/doc/boot_sectors.txt](https://dev.lovelyhq.com/libburnia/libisofs/raw/HEAD/doc/boot_sectors.txt)
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for technical details.)
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Examples how to get an impression of the boot equipment of existing ISO 9660
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images are on the wiki page about xorriso
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[commands -report_system_area and -report_el_torito](Reportsystemarea).
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##### How to enable booting from USB stick ? <A NAME="isohybrid">
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In most cases, ISOs are prepared for PC-BIOS to boot the ISOLINUX boot loader.
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This boot loader is normally started from CD, DVD or BD media via an El Torito
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boot record. But if the ISO image resides on an USB stick or another
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hard-disk-like device, then PC-BIOS ignores El Torito and rather expects a
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Master Boot Record (MBR). Both boot record types can reside in the same ISO
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image. Therefore it is possible to create an MBR that starts the boot image
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file of ISOLINUX which is already target of the El Torito boot record.
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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
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an MBR already when producing the ISO image. See in
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[manual page of xorriso](http://www.gnu.org/software/xorriso/man_1_xorriso.html)
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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 [Wikipedia on MBR](http://en.wikipedia.org/wiki/Master_boot_record) for
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general information about PC-DOS Master Boot Records, and
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[ISOLINUX wiki](http://syslinux.zytor.com/wiki/index.php/ISOLINUX) 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 [homepage of GNU GRUB 2](http://www.gnu.org/software/grub/)
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for general information.
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EFI firmware in its native mode boots by El Torito from CD, DVD or BD media,
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and by partition table from USB stick or hard disk. Both, El Torito and
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partition table, point to a FAT filesystem image, the EFI System Partition.
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The partiton table may be either a DOS-style MBR partition table or a
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[GUID Partition Table](https://en.wikipedia.org/wiki/GUID_Partition_Table).
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The x86 program program in the MBR is ignored by EFI, which rather starts
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a program from the FAT directory "\EFI\BOOT". The name of the program file
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depends on the processor architecture: BOOTX64.EFI, BOOTIA32.EFI, BOOTARM.EFI,
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BOOTAA64.EFI for x86 64 bit, x86 32 bit, ARM 32 bit, and ARM 64 bit,
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respectively.
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The boot equipment for other systems may well work from USB stick too.
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But libburnia project has no tangible information about this.
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##### What is partition offset feature all about? <A NAME="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.
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The `grub-mkrescue` MBR on the other hand has partition 1 start at byte 512,i
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which makes it unmountable. Only the unpartitioned base device can be mounted.
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(On GNU/Linux
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e.g. `/dev/sdb` is the base device whereas `/dev/sdb1` is its 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 [Partition Offset Wiki](PartitionOffset)
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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 ? <A NAME="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 not yet fully understood. 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 ? <A NAME="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 git versions of these files:
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[libburn/libburn.h](https://dev.lovelyhq.com/libburnia/libburn/raw/HEAD/libburn/libburn.h) ,
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[libisofs/libisofs.h](https://dev.lovelyhq.com/libburnia/libisofs/raw/HEAD/libisofs/libisofs.h) ,
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[libisoburn/libisoburn.h](https://dev.lovelyhq.com/libburnia/libisoburn/raw/HEAD/libisoburn/libisoburn.h) ,
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[libisoburn/xorriso.h](https://dev.lovelyhq.com/libburnia/libisoburn/raw/HEAD/xorriso/xorriso.h)
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##### I want to write a GUI on the top of libburnia libraries. Any pointers or recommendations ? <A NAME="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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[man 1 xorriso](http://www.gnu.org/software/xorriso/man_1_xorriso.html)
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can be performed by a corresponding C function that is defined in
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[xorriso.h](https://dev.lovelyhq.com/libburnia/libisoburn/raw/HEAD/xorriso/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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[See below](#xorriso_dialog_mode).
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The script
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[xorriso-tcltk](https://dev.lovelyhq.com/libburnia/libisoburn/raw/HEAD/frontend/xorriso-tcltk)
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demonstrates this approach. It is part of the
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libisoburn release tarball and of the GNU xorriso tarball.
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The known existing GUIs
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[Xfburn](http://goodies.xfce.org/projects/applications/xfburn),
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[Brasero](http://projects.gnome.org/brasero/),
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[FlBurn](http://flburn.sourceforge.net/)
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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 ? <A NAME="example_links">
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[xorriso examples](http://www.gnu.org/software/xorriso/man_1_xorriso.html#EXAMPLES) ,
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[cdrskin examples](http://scdbackup.sourceforge.net/man_1_cdrskin_devel.html#EXAMPLES) ,
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[libburner.c a minimal but complete burn program](https://dev.lovelyhq.com/libburnia/libburn/raw/HEAD/test/libburner.c).
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##### What personalities are supported by xorriso ? <A NAME="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 can 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 ? <A NAME="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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The script
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[xorriso-tcltk](https://dev.lovelyhq.com/libburnia/libisoburn/raw/HEAD/frontend/xorriso-tcltk)
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demonstrates this approach. It is part of the
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libisoburn release tarball and of the GNU xorriso tarball.
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##### Why is every second release missing ? <A NAME="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 git version
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of `libisoburn/doc/faq.wiki`. When done, paste it into the wiki editor.
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