elilovars.txt

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Information related to variable support in ELILO
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(c) 2002-2003 Hewlett Packard Co
    Contributed by Stephane Eranian <[e-mail]>

    Last updated: 06/13/2002

As of version 3.2, elilo has internal variables which can be programmed
by any module inside the bootloader code. These variables are used
to parametrize some of the arguments passed on the kernel command line.

The value of a variable is a Unicode string. Variables names are composed
of a single Unicode character, such as 'I' for instance. Variable names
are case sensitive. Elilo has support for 52 variables: A-Z and a-z. 

The '%' sign is used to name a variable. For instance, '%I' indicates 
variable 'I'. If '%I'  is present on the command line to the kernel, 
it will be replaced (string replacement) with the value (a string) of 'I'. 
By default, the Elilo core does not assign any values to any variables. 
It is up to each module to do so. When a variable is not used, its content 
is the empty string "", which means that the '%d' notation, for instance, will 
be replaced with the empty string.

Let us look at an example:
  Supposing that the following variables are defined:
	'I'	-> "192.168.2.5"
	'G'	-> "192.168.2.1"
	'M'	-> "255.255.255.0"
	'z'	-> ""

  Then a command line of this form (provided as an append= option in elilo.conf):

        root=/dev/nfs nfsroot=15.4.88.178:/mnt2 ip=%I:%z:%G:%N:jung:eth0:on

  Would pass the following to the kernel:

        root=/dev/nfs nfsroot=15.4.88.178:/mnt2 ip=192.168.2.5::192.168.2.1:255.255.255.0:jung:eth0:on

Of course, the meaning of each variable is up to each individual module, the
names used here are not necessarily representative of the actual names used
by elilo.

Some choosers, (such as simple) have support to print the list of
defined variables. For instance, in simple (the default chooser) you
can press '%' to see the list of defined variables.

Variables can be useful when netbooting, for instance, to get the 
dynamically assigned IP, netmask, and gateway addresses.

In case the % character needs to be passed to the kernel, it is possible
to "despecialize" a character using the & symbol in front of it.

See netbooting.txt for more information on this.