53 lines
2.2 KiB
Text
53 lines
2.2 KiB
Text
Information related to variable support in ELILO
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(c) 2002-2003 Hewlett Packard Co
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Contributed by Stephane Eranian <eranian@hpl.hp.com>
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Last updated: 06/13/2002
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As of version 3.2, elilo has internal variables which can be programmed
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by any module inside the bootloader code. These variables are used
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to parametrize some of the arguments passed on the kernel command line.
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The value of a variable is a Unicode string. Variables names are composed
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of a single Unicode character, such as 'I' for instance. Variable names
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are case sensitive. Elilo has support for 52 variables: A-Z and a-z.
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The '%' sign is used to name a variable. For instance, '%I' indicates
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variable 'I'. If '%I' is present on the command line to the kernel,
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it will be replaced (string replacement) with the value (a string) of 'I'.
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By default, the Elilo core does not assign any values to any variables.
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It is up to each module to do so. When a variable is not used, its content
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is the empty string "", which means that the '%d' notation, for instance, will
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be replaced with the empty string.
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Let us look at an example:
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Supposing that the following variables are defined:
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'I' -> "192.168.2.5"
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'G' -> "192.168.2.1"
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'M' -> "255.255.255.0"
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'z' -> ""
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Then a command line of this form (provided as an append= option in elilo.conf):
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root=/dev/nfs nfsroot=15.4.88.178:/mnt2 ip=%I:%z:%G:%N:jung:eth0:on
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Would pass the following to the kernel:
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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
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Of course, the meaning of each variable is up to each individual module, the
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names used here are not necessarily representative of the actual names used
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by elilo.
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Some choosers, (such as simple) have support to print the list of
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defined variables. For instance, in simple (the default chooser) you
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can press '%' to see the list of defined variables.
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Variables can be useful when netbooting, for instance, to get the
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dynamically assigned IP, netmask, and gateway addresses.
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In case the % character needs to be passed to the kernel, it is possible
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to "despecialize" a character using the & symbol in front of it.
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See netbooting.txt for more information on this.
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