Some users may need specific support because of e.g. some visual impairment. USB braille displays are detected automatically (not serial displays connected via a serial-to-USB converter), but most other accessibility features have to be enabled manually. On machines that support it, the boot menu emits a beep when it is ready to receive keystrokes. Some boot parameters can then be appended to enable accessibility features (see also Section 5.1.5, “The Boot Screen”). Note that on most architectures the boot loader interprets your keyboard as a QWERTY keyboard.
The Ubuntu installer supports several front-ends for asking questions, with
varying convenience for accessibility: notably, text
uses plain text while newt
uses text-based dialog
boxes. The choice can be made at the boot prompt, see the documentation for
DEBIAN_FRONTEND
in Section 5.3.2, “Ubuntu Installer Parameters”.
USB braille displays should be automatically detected. A textual version
of the installer will then be automatically selected, and support for the
braille display will be automatically installed on the target system.
You can thus just press Enter at the boot menu.
Once brltty
is started, you can choose a braille
table by entering the preference menu. Documentation on key
bindings for braille devices is available on the brltty
website.
Serial braille displays cannot safely be automatically detected
(since that may damage some of them). You thus need to append the
brltty=
boot parameter to tell driver
,port
brltty
which driver and port it
should use. driver
should be replaced by the
two-letter driver code for your terminal (see the
BRLTTY manual).
port
should be replaced by the name of the
serial port the display is connected to, ttyS0
is
the default, ttyUSB0
can be typically used when using a serial-to-USB converter.
A third parameter can be provided, to choose the name of the
braille table to be used (see the BRLTTY
manual); the English table is the default. Note that the table can
be changed later by entering the preference menu. A fourth parameter
can be provided to pass parameters to the braille driver, such as
protocol=foo
which is needed for some rare models.
Documentation on key
bindings for braille devices is available on the brltty
website.
Support for software speech synthesis is available on all installer images which
have the graphical installer, i.e. all netinst, CD and DVD images, and the
netboot gtk variant. It can be activated by selecting it in the
boot menu by typing s
Enter. The textual version
of the installer will then be automatically selected, and support for software
speech synthesis will be automatically installed on the target system.
The first question (language) is spoken in english, and the remainder
of installation is spoken in the selected language (if available in
espeak
).
The default speech rate is quite slow. To make it faster, press CapsLock+6. To make it slower, press CapsLock+5. The default volume should be medium. To make it louder, press CapsLock+2. To make it quieter, press CapsLock+1. To get more details on the browsing shortcuts, see the Speakup guide.
Support for hardware speech synthesis devices is available on all installer images which have the graphical installer, i.e. all netinst, CD and DVD images, and the netboot gtk variant. You thus need to select a “Graphical install” entry in the boot menu.
Hardware speech synthesis devices cannot be automatically detected. You
thus need to append the
speakup.synth=
boot parameter to tell driver
speakup
which driver it should
use. driver
should be replaced by the driver code
for your device (see driver code
list). The textual version of the installer will then be
automatically selected, and support for the speech synthesis device will be
automatically installed on the target system.
Some accessibility devices are actual boards that are plugged inside the
machine and that read text directly from the video memory. To get them
to work framebuffer support must be disabled by using the
vga=normal
fb=false
boot parameter. This will however reduce the number of available languages.
If desired a textual version of the bootloader can be activated before adding
the boot parameter by typing h
Enter.
For users with low vision, the installer can use a high-contrast
color theme that makes it more readable. To enable it, append the
theme=dark
boot parameter.
For users with low vision, the graphical installer has a very basic zoom support: the Control++ and Control+- shortcuts increase and decrease the font size.
Alternatively, Ubuntu can be installed completely automatically by using preseeding. This is documented in Appendix B, Automating the installation using preseeding.
Documentation on accessibility of the installed system is available on the Debian Accessibility wiki page.