Adding BRLTTY to a Red Hat Linux Install CD
===========================================
Written during April, 2004, by Dave Mielke <dave@mielke.cc>.
Quick Start
-----------
The script "rhmkiso" can be used to add BRLTTY to a RedHat or Fedora install
CD. Here's how to use it.
First: Log in as (or su to) root. This is because the script uses a loopback
mount. You'll probably also need to be root in order to write the resultant
image to a CD as well.
Second: Create an empty directory and change to it.
mkdir work
cd work
Third: Copy or download the image of the installer CD ("boot.iso") for the
desired RedHat or Fedora release, or the image for the first CD of the full
installation set ("disc1.iso"), into the current directory.
cp /path/to/boot.iso .
Fourth: Copy or download the tarball for the desired BRLTTY release into the
current directory.
cp /path/to/brltty-3.5.tar.gz .
Fifth: Run the "rhmkiso" script with no options or parameters.
rhmkiso
Sixth: You should now have a new file, "brltty.iso", in the current directory.
Write this modified image to a CD.
cdrecord -v dev=0,0,0 -data brltty.iso
If you're using a rewritable CD then you should erase it first.
cdrecord -v dev=0,0,0 blank=fast
For more information on writing to a CD, please check the CD-Writing HOWTO at:
http://tldp.org/HOWTO/CD-Writing-HOWTO.html
Seventh: Boot from the CD you've just written, and wait a few seconds after it
begins to spin in order to give the boot loader enough time to get started and
to present its initial prompt. Then enter:
text brltty=<driver>,<device>,<table>
e.g.
text brltty=ht,ttyS1,de
You can omit any operand, allowing it to default, simply by not specifying it.
You also needn't specify any trailing commas resulting from omitted operands.
text brltty=ht,ttyS1,
text brltty=ht,ttyS1
text brltty=ht,
text brltty=ht
text brltty=ht,,de
text brltty=ht,,
The <driver> operand is the two-letter identifier of the driver for your
braille display. It's the only required operand. See the -b option (below) for
further details.
The <device> operand is the device to which your braille display is connected.
It's optional, and defaults to the primary serial port ("/dev/ttyS0"). If your
display is connected to a serial port then specify either the name (e.g.
"ttyS1") of or the path (e.g. "/dev/ttyS1") to the corresponding device. If
it's connected to the USB then specify "usb:" (the trailing colon is
important).
The <table> operand is the text translation table you wish to use. It's
optional, and defaults to "nabcc" (North American Braille Computer Code). See
the "text.*.tbl" files in the "BrailleTables" subdirectory of BRLTTY's source
tree for alternatives. See the -t option (below) for further details.
The Details
-----------
The "rhmkiso" script can add BRLTTY to either a RedHat or a Fedora install CD.
It can be applied either to the basic installer CD or to the first CD of the
full installation set, and makes the following modifications to the image:
* BRLTTY is added (all drivers, all tables).
* The timeout for the initial boot loader prompt is disabled.
* The default kernel configuration to be booted is changed to "text".
* The use of frame buffers for the "text" consoles is disabled.
For rescue images, the following additional modifications are made:
* Text consoles are used when "rescue" is selected.
* The use of frame buffers for the "rescue" consoles is disabled.
Although its defaults are what usually needs to be done, the "rhmkiso" script
offers a number of options so that you can customize what it does. It's general
invocation syntax is:
rhmkiso [-option ...]
The following options are provided:
-i file The original (input) image (default: boot.iso).
-o file The modified (output) image (default: brltty.iso).
-a file The BRLTTY archive (default: check current directory).
-b driver,... The braille driver(s) to include (default: all).
-t file The text translation table to build in (default: nabcc).
-s Invoke an interactive shell to inspect the modified image.
-h Display usage information and exit.
The -i option specifies the location of the distribution-supplied original
(input) image which is to be modified. Either a relative or an absolute path
may be supplied. It defaults to "boot.iso" (the usual name for the basic
installer CD image).
The -o option specifies the location of the file which is to contain the
modified (output) image which the script will create. Either a relative or an
absolute path may be supplied. It defaults to "brltty.iso".
The -b option specifies which braille display drivers will be linked into the
brltty executable as opposed to being built as dynamically loadable shared
objects. If more than one driver is specified then their specifiers must be
separated from one another by a comma. Either the two-letter identifier or the
proper name (full or abbreviated) for each driver must be supplied. If a driver
specifier is prefixed by a minus sign (-) then that driver is excluded from the
build. The first non-excluded driver in the list is the default driver. The
word "all", if used instead of a driver specifier as the last item in the list,
causes all the remaining drivers to be implicitly appended to the list in no
specific order (or, if preceded by a minus sign, to be excluded from the
build). The default is "all", i.e. all of the drivers (in no particular order
so the default is unpredictable) are linked in.
The -t option specifies which text translation table is to be built into the
brltty executable. If a relative path is supplied then it's anchored at the
"BrailleTables" subdirectory within BRLTTY's source tree. Since any of BRLTTY's
own tables can also be specified when the image is booted, the primary use of
this option is to specify the absolute path to a user-defined table outside
BRLTTY's source tree. The ".tbl" extension is optional. If a simple file name,
i.e. one of BRLTTY's own tables, is being supplied then the "text." prefix is
also optional. The default is "nabcc" (North American Braille Computer Code).
The -s option causes an interactive shell to be invoked after all of the
modifications to the files within the image have been made but before the CD
image is created. This gives you an opportunity to inspect what the script has
done. Your login shell, i.e. the one pointed to by the $SHELL environment
variable, is used; if it's not set then "/bin/sh" is assumed.
The script uses a lot of temporary file space to do its job, especially if the
first CD of the full installation set is being used. This is because it needs
to work with a complete extracted copy of the files within the image. If
there's not enough space in "/tmp" then you can direct the script to use
another directory via the $TMPDIR environment variable.
The script uses a loopback mount to access the files within the original CD
image. This means that it must be run as root.
