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/**
@author Mario Danic, Vreixo Formoso, Thomas Schmitt
@mainpage Libisoburn Documentation Index
@section intro Introduction
Libburnia is an open-source project for reading, mastering and writing
optical discs. This page is about its capability to read, manipulate, and
write ISO 9660 filesystems with Rock Ridge extensions. Media can be optical
media or filesystem objects.
Our scope is currently Linux 2.4 and 2.6, or FreeBSD, or OpenSolaris.
libisoburn is an add-on to libburn and libisofs which coordinates both and
also allows to grow ISO-9660 filesystem images on multi-session media as well
as on overwriteable media via the same API.
All media peculiarities are handled automatically.
xorriso is an application of all three libraries which creates, loads,
manipulates and writes ISO 9660 filesystem images with Rock Ridge extensions.
Manipulation is not only adding or overwriting of files but also deletion,
renaming, and attribute changing. An incremental backup feature is provided.
The xorriso features are accessible via built-in command interpreters and
via a C language API.
SONAME:
libisoburn.so.1 (since 0.1.0, February 2008).
@section using Using the libraries
Our build system is based on autotools.
User experience tells us that you will need at least autotools version 1.7.
To build libisoburn go into its toplevel directory and execute:
- ./bootstrap (needed if you downloaded from SVN)
- ./configure
- make
To make the library and the xorriso application accessible for running resp.
software development:
- make install
For direct use as command line tool use the xorriso binary which among many
other features provides a mkisofs emulation via command "-as mkisofs".
See man page xorriso/xorriso.1 or GNU info document xorriso/xorriso.info.
If you want to link an own application with libisoburn, you have
two alternative APIs for choice:
- libisoburn, together with libburn and libisofs.
- xorriso, a complete representation of xorriso command line options.
It encapsulates the three lower level libraries.
Calls of both API families shall not be mixed.
For a description of the lbisoburn API read libisoburn/libisoburn.h
See file README for download and installation of a release tarball.
You will also have to install and understand the two libraries of the
Libburnia project which provide fundamental services:
libburn is the library by which preformatted data get onto optical media.
See libburn/libburn.h for its API description.
libisofs is the library to handle ISO 9660 filesystems with Rock Ridge
extensions. Its API is described in libisofs/libisofs.h .
For xorriso features see its man page xorriso/xorriso.1 or
its GNU info document xorriso/xorriso.info.
For the corresponding C language API see libisoburn/xorriso.h (resp.
xorriso/xorriso.h in the build directory).
The implementation this API is part of libisoburn.
The xorriso command line tool gets installed as dynamically linked
binary together with libisoburn.
There is also a statically linked release named GNU xorriso.
See xorriso/README_gnu_xorriso for its download and installation.
*/

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

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The partition offset feature of libisofs can produce ISO 9660 images which bear
a quite conventional partition table if copied onto a USB stick. The first
partition marks the size of the ISO image but starts at a non-zero address.
Thus it marks a small part of the device as unclaimed by partitions and
available for storing boot loader code.
Nevertheless the USB stick is mountable via its overall device file as well as
via the partition device file. E.g. on GNU/Linux: /dev/sdb and /dev/sdb1.
This is achieved by two distinct sets of meta-data which refer to the same
file content.
The dual-mount feature supports Rock Ridge and eventually Joliet too.
It is capable of multi-session.
Currently only offset 32 kB seems to make sense. Smaller offsets are prohibited
by fundamental assumptions of libisofs and libisoburn. Larger offsets would
extend the unclaimed area into vital blocks of the ISO image.
--------------------------------------------------------------------------
Meanwhile Debian
[http://cdimage.debian.org/cdimage/daily-builds/daily/current/ daily]
and [http://cdimage.debian.org/cdimage/weekly-builds/ weekly] builds make
use of this feature with their bootable ISO images for i386 and amd64. E.g.
[http://cdimage.debian.org/cdimage/daily-builds/daily/current/i386/iso-cd/debian-testing-i386-businesscard.iso debian-testing-i386-businesscard.iso].
--------------------------------------------------------------------------
Example:
Testing mountability and ISOLINUX bootability from USB stick and CD.
Overview:
The test image was derived from one year old RIPLinux-9.3-non-X.iso which
has an isohybrid MBR. Syslinux version seems to be 3.82. That MBR and the file
tree from the mounted RIPLinux image was used to build a new ISO image
with 16 * 2kB partition offset. Isohybrid MBR patching was done by xorriso.
Details:
The first 32 kB of an ISO 9660 image are called System Area and may host any
byte pattern. In the case of RIPLinux-9.3-non-X.iso only the first 512 bytes
are non-zero. But to avoid any assumptions, all 32 kB get copied here.
{{{
dd if=RIPLinux-9.3-non-X.iso bs=1K count=32 of=RIPLinux-9.3-non-X.sysarea
}}}
The files of the image are made accessible for reading
{{{
mount -o loop RIPLinux-9.3-non-X.iso /mnt
}}}
A new ISO image gets composed. The first three lines of arguments are taken
from the prescriptions of ISOLINUX wiki and adapted to the names used in
RIPLinux-9.3-non-X.iso.
Option -isohybrid-mbr imports the copied System Area and patches the MBR
according to rules published by hpa on Syslinux mailing list.
Option -partition_offset 16 causes the first partition to start at 2 kB block
number 16. It also prepares the image to be mountable by this partition, too.
{{{
xorriso -as mkisofs \
-o new_image.iso \
-b boot/isolinux/isolinux.bin -c boot/boot.cat \
-no-emul-boot -boot-load-size 4 -boot-info-table \
-isohybrid-mbr RIPLinux-9.3-non-X.sysarea \
-partition_offset 16 \
/mnt
}}}
The image was copied onto a USB stick
{{{
dd if=new_image.iso of=/dev/sdc
}}}
and plugged into a Debian system.
{{{
fdisk -lu /dev/sdb
}}}
yields
{{{
Device Boot Start End Blocks Id System
/dev/sdb1 * 64 119215 59576 17 Hidden HPFS/NTFS
}}}
I can mount /dev/sdb and /dev/sdb1 alike:
{{{
mount /dev/sdb1 /mnt1
mount -o loop /dev/sdb /mnt
}}}
-o loop avoids failure with "mount: /dev/sdb already mounted or /mnt busy".
A comparison by
{{{
diff -r /mnt /mnt1
}}}
reports no difference.
Human readable files look ok.
Test-reading all content by
{{{
tar cf - /mnt | wc
}}}
yields a reasonable byte count of 60743680 and no errors.
The machine boots RIPLinux from this USB stick with no visible problems.
It can then mount /dev/sdb as well as /dev/sdb1.
The ISO image boots from CD too.
Mounting the partition can be simulated with an image file on hard disk by
cutting off the first partition_offset blocks of 2 KB:
{{{
dd if=new_image.iso of=partition_image.iso bs=2048 skip=16
mount -o loop partition_image.iso /mnt1
}}}
--------------------------------------------------------------------------
Another test was made with GRUB 2 by downloading
{{{
bzr branch http://bzr.savannah.gnu.org/r/grub/trunk/grub
}}}
Before building GRUB 2, the file
{{{
util/grub-mkrescue.in
}}}
was edited to replace in the options of the xorriso command:
{{{
--protective-msdos-label
}}}
by
{{{
-partition_offset 16 -no-pad --no-emul-toc
}}}
Then GRUB 2 was built and installed.
The resulting image from
{{{
./grub-mkrescue -o image.iso
}}}
was put onto USB stick. It passed the same tests on Debian
as above RIPLinux example. It boots to a GRUB prompt.
Due to options -no-pad --no-emul-toc the image is about 300 kB smaller than
the image produced by original grub-mkrescue. Else it would have grown by
about 130 kB. The mkisofs emulation of newer versions of xorriso has
--no-emul-toc as default. Thus the overhead would only be about 50 kB.
--------------------------------------------------------------------------
Open questions:
- Shall the partition of an isohybrid image be marked bootable ?
Currently xorriso keeps the 0x80 mark of an eventually imported MBR
resp. the 0x80 mark which xorriso eventually sets by its own MBR
preparations.
- If not to be marked bootable:
What equipment would the partition need to justify having the mark ?
- I am still puzzled by the cylinder-head-sector ambiguity. How does a reader
of the partition table determine the numbers for heads/cylinder and
sectors/head ?
fdisk tells about my /dev/sdb
{{{
105 heads, 17 sectors/track, 2193 cylinders, total 3915776 sectors
}}}
My partiton table rather was computed with 255 heads/cylinder, 63 sectors/head
Debian does not mind the difference. (It uses the 32 bit LBAs, i assume.)
------------------------------------------------------------------------
Application:
The partition offset feature can be controlled by libisofs API call
{{{
int iso_write_opts_set_part_offset(IsoWriteOpts *opts,
uint32_t block_offset_2k,
int secs_512_per_head,
int heads_per_cyl);
}}}
resp. by libisoburn calls
{{{
int isoburn_igopt_set_part_offset(struct isoburn_imgen_opts *opts,
uint32_t block_offset_2k,
int secs_512_per_head, int heads_per_cyl);
int isoburn_igopt_get_part_offset(struct isoburn_imgen_opts *opts,
uint32_t *block_offset_2k,
int *secs_512_per_head, int *heads_per_cyl);
}}}
resp. by xorriso options
{{{
-boot_image any partition_offset=(2kb_block_adr)
-boot_image any partition_sec_hd=(number)
-boot_image any partition_hd_cyl=(number)
-as mkisofs ... -partition_offset (2kb_block_adr) ...
}}}
As stated above, an offset larger than 16 would expose vital parts of the
ISO image as unclaimed space. Values smaller than 16 are not accepted.
So use either an offset of 16 blocks or keep the feature disabled by
offset 0.