eliloalt.txt

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Information related to the eliloalt Linux tool
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(c) 2002-2003 Hewlett Packard Co
    Contributed by Stephane Eranian <[e-mail]>

    Last updated: March 1st, 2002


The elilo alternate image feature uses an EFI variable called EliloAlt. 
The content of this variable is a UNICODE string containing a kernel
image file and its command line options. The variable has a NULL GUID.

To create, read, or modify the variable you need to use the EFI variable
service and the SetVariable() or GetVariable() interface. The service
is available when EFI is in boot service mode, i.e., prior to loading
the kernel but it is also available at runtime when the Linux kernel
has taken over the control of the machine. 

In order to modify the variable, you can either write a small EFI applications
or use the Linux/ia64 interface to the EFI variables which use the /proc filesystem.

The elilalt tool included in this package uses the /proc interface to EFI variables
to create, read, or modify the EliloAlt variable. This tool is a Linux/ia64 application
and NOT an EFI application.


Because modiyfing the EliloAlt can influence how the machine is booted, you must
be root to run the program, even when you simply want to read the content of
the variable.

Eliloalt provides the following options:

	-h, --help              display this help and exit
	--version               output version information and exit
	-s, --set cmdline       set elilo alternate variable to cmdline
	-p, --print             print elilo alternate variable
	-d, --delete            print elilo alternate variable

1/ Creation of the variable

	To create the variable you can type:

	# eliloalt -s "vmlinuz-2.4.9 root=/dev/sdb2 hdc=ide-scsi"

	It is VERY important to use quotes to make sure that the entire list of arguments is 
	treated as a single argument to the program. Otherwise only the first element 
	(here vmlinuz-2.4.9) will be used.


2/ Printing the content of the variable

	To print the content of the variable you need to type:

	# eliloalt -p
	EliloAlt="vmlinuz-2.4.9 root=/dev/sdb2 hdc=ide-scsi"

3/ Modifying the variable

	You can simply use the -s option:
	# eliloalt -s "vmlinuz-2.4.18 root=/dev/sdb2"
	# eliloalt -p
	EliloAlt="vmlinuz-2.4.18 root=/dev/sdb2"
	
3/ Deleting the variable

	You must use the -d option:
	# eliloalt -p
	EliloAlt="vmlinuz-2.4.18 root=/dev/sdb2"
	# eliloalt -d
	# eliloalt -p
	variable not defined
	
	Keep in mind that the variable is automatically deleted by elilo if:
		- the checkalt option is specified in the config file 
	    OR
		- the -a is used on the command line