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FILO is currently maintained by Stefan Reinauer. Go to for up-to-date information.

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[   ]CHANGES31-Oct-2003 22:09 2.5K 
[   ]FAQ30-Oct-2003 01:33 418  
[   ]filo-0.1.tar.bz220-Aug-2003 20:52 77K 
[   ]filo-0.2.tar.bz219-Sep-2003 21:21 80K 
[   ]filo-0.3.tar.bz207-Oct-2003 20:26 87K 
[   ]filo-0.4.1.tar.bz230-Oct-2003 01:42 96K 
[   ]filo-0.4.2.tar.bz214-May-2004 12:16 96K 
[   ]filo-0.4.tar.bz215-Oct-2003 20:20 95K 

This is FILO, a bootloader which loads boot images from local filesystem,
without help from legacy BIOS services.

Expected usage is to flash it into the BIOS ROM together with LinuxBIOS.


    - Supported boot devices: IDE hard disk and CD-ROM, and system memory (ROM)
    - Supported filesystems: ext2, fat, jfs, minix, reiserfs, xfs, and iso9660
    - Supported image formats: ELF and [b]zImage (a.k.a. /vmlinuz)
    - Supports boot disk image of El Torito bootable CD-ROM
    - Supports loading image from raw device with user-specified offset
    - Console on VGA + keyboard, serial port, or both
    - Line editing with ^H, ^W and ^U keys to type arbitrary filename to boot
    - Full support for the ELF Boot Proposal (where is it btw, Eric?)
    - Auxiliary tool to compute checksum of ELF boot images
    - Full 32-bit code, no BIOS calls


    Only i386 PC architecture is currently supported.

    x86-64 (AMD 64) machines in 32-bit mode should also work.
    (It looks like LinuxBIOS uses 32-bit mode and Linux kernel does
    the transition to 64-bit mode)

    I'm using a VIA EPIA 5000 mini-ITX board, with a 2.5" IDE hard disk
    and a 32x CD-RW, for testing, and Bochs and VMware for development.

    Recent version of GNU toolchain is required to build.
    I have tested with Debian/woody (gcc 2.95.4, binutils,
    make 3.79.1) and Debian/sid (gcc 3.3.2, binutils,
    make 3.80).


    First invocation of make creates the default Config file.
	$ make
    Edit this file as you like. It's fairly straightforward (I hope).
	$ vi Config
    Then running make again will build filo.elf, the ELF boot image of FILO.
	$ make

    Use filo.elf as your payload of LinuxBIOS, or a boot image for

    If you enable MULTIBOOT_IMAGE option in Config, you can
    also boot filo.elf from GNU GRUB or other Multiboot bootloader.
    This feature is intended for testing or development purpose.


    When FILO starts, it displays "boot:" prompt.
    At "boot:" prompt, type the name of your boot image, and optionally
    the kernel parameter, in the form:
    for example:
	boot: hda1:/vmlinuz root=/dev/hda1

    Notation of DEVICE for IDE disk and CD-ROM is same as in Linux
    (eg. hda1 means the first partition of master device on primary 
    IDE channel).

    FILENAME can be standard bzImage/zImage (vmlinuz) Linux kernels,
    Linux-compatible images such as memtest.bin of Memtest86,
    and any bootable ELF images, which include Linux kernel converted
    by mkelfImage, Etherboot .elf and .zelf, Memtest86, FILO itself, etc.

    If AUTOBOOT_FILE is set in Config, FILO tries to boot this file
    first, and falls back to boot: prompt if it fails.

    If AUTOBOOT_DELAY is also set, FILO waits for specified time in
    seconds before booting AUTOBOOT_FILE. If <Esc> key is pressed
    during this time period, automatic boot is canceled.
    Pressing <Enter> key also cancels the delay, but in this case
    AUTOBOOT_FILE is booted immediately.

    Even if AUTOBOOT_DELAY is not set, automatic boot can be disabled
    by pressing <Esc> key beforehand.

    FILO can also load separate initrd images along with vmlinuz
    kernels. (For ELF kernel, initrd images are embedded into the
    ELF file and cannot be altered).
    To do so, add "initrd=NAME" parameter to the kernel command line.
    NAME uses the same notation as kernel image name.
    (eg. boot: hda1:/vmlinuz initrd=hda1:/root.gz root=/dev/ram)

    To boot an image in the BIOS flash (or whatever is mapped in the system
    memory space), use the notation "mem@OFFSET[,LENGTH]", like:
	boot: mem@0xfffe0000
    In this example, it loads the boot image from the last 128KB of BIOS

    The same notation can be used with IDE devices, eg:
	boot: hda@512,697344 initrd=hda@1M,4M
    In this case the 697344 bytes starting from second sector of IDE drive
    is loaded as kernel, and 4M bytes of offset 1M bytes of the same disk
    is loaded as initrd.
    Note that when you load vmlinuz kernel or initrd this way,
    you must specify the LENGTH parameter. You can omit it for ELF
    images since they have segment length internally.
    OFFSET and LENGTH parameters must be multiple of 512.


    If you have problem with FILO, set DEBUG_ALL in Config and send its 
    console output to me at <>.


    Filesystem code is taken from GNU GRUB and patches for it.
    IDE driver is originally taken from Etherboot.
    Steve Gehlbach wrote the original bzImage loader for FILO.

    Besides, I have taken pieces of code and/or learned concepts
    from various standalone programs, including GNU GRUB, Etherboot,
    polled IDE patch by Adam Agnew, Memtest86, LinuxBIOS, and Linux.
    I must say thanks to all the developers of these wonderful software,
    especially to Eric Biederman for his great development work in this area.


    Copyright (C) 2003 by SONE Takeshi <> and others.
    This program is licensed under the terms of GNU General Public License.
    See the COPYING file for details.