Using GRUB
Using GRUB
The GRUB homepage can be found at http://www.gnu.org/software/grub/grub.en.html.
This tutorial was written by Chris Giese and is also availible at his site.
================================================================ References ================================================================ This information was gleaned from my own experiments with GRUB and from the following posts to alt.os.development: Subject: Re: generic bootloader question Newsgroups: alt.os.development From: "Marv"Date: Sat, 7 Apr 2001 23:35:20 +0100 References: Message-ID: Subject: Re: Grub multiboot example Newsgroups: alt.os.development From: "Marv" Date: Mon, 4 Jun 2001 17:21:17 +0100 References: Message-ID: Subject: Re: Grub multiboot example Newsgroups: alt.os.development From: "Mike Wimpy" Date: Thu, 7 Jun 2001 22:17:51 -0700 References: Message-ID: Subject: Re: grub coff (solved it!) Newsgroups: alt.os.development From: "Mark & Candice White" Date: Sun, 16 Sep 2001 10:57:34 GMT References: Message-ID: ================================================================ Getting GRUB ================================================================ Source code: ftp://alpha.gnu.org/gnu/grub/grub-0.90.tar.gz Binaries: ftp://alpha.gnu.org/gnu/grub/grub-0.90-i386-pc.tar.gz DOS and Windows users will need PARTCOPY or RAWRITE: http://www.execpc.com/~geezer/johnfine/index.htm#zero http://uranus.it.swin.edu.au/~jn/linux/rawwrite.htm http://www.tux.org/pub/dos/rawrite/ ================================================================ Building GRUB ================================================================ UNIX ---- configure ; make (...I think...) DOS and Windows --------------- (ha! forget it) ================================================================ Installing GRUB on a floppy with no filesystem ================================================================ 1. Get the GRUB binaries (files "stage1" and "stage2") 2. Concatenate the files "stage1" and "stage2" into one file: (DOS) copy /b stage1 + stage2 boot (UNIX) cat stage1 stage2 >boot 3. Write the file "boot" directly to the floppy disk: (DOS) rawrite boot a: -OR- (DOS) partcopy boot 0 168000 -f0 (UNIX) cat boot >/dev/fd0 PARTCOPY will give an error message because the file "boot" is much shorter than 0x168000 bytes, but this is OK. ================================================================ Installing GRUB on a floppy with a filesystem ================================================================ 1. Make a bootable GRUB floppy with no filesystem, as described above. 2. Copy the files "stage1" and "stage2" to a second floppy disk, one formatted with a filesystem that GRUB recognizes. To use the GRUB "setup" command, these files must be stored in subdirectory "/boot/grub": (DOS) mkdir a:\boot mkdir a:\boot\grub copy stage1 a:\boot\grub copy stage2 a:\boot\grub (UNIX) mount /dev/fd0 /mnt mkdir /mnt/boot mkdir /mnt/boot/grub cp stage1 /mnt/boot/grub cp stage2 /mnt/boot/grub 3. After GRUB is installed on floppy disk #2, the file "stage2" must not be modified, deleted, defragged, or moved. If it is modified in any way, the disk will no longer be bootable. To prevent this, make the file read-only: (DOS) attrib +r +s stage2 (UNIX) chmod a-w stage2 The DOS command above makes "stage2" a System file as well as Read-only. This is needed to protect against DEFRAG. NOTE: File "stage1" will be copied into the bootsector. If this file is moved or deleted after GRUB is installed, the disk will still be bootable. 4. Boot your computer from the floppy with GRUB but no filesystem. At the GRUB prompt, eject this floppy and insert the formatted floppy disk (with the filesystem and "stage1" and "stage2" files, possibly in directory "/boot/grub". 5a. If files "stage1" and "stage2" are stored in "/boot/grub" on disk #2, you can install GRUB on disk #2 simply by typing: setup (fd0) This is apparently equivalent to this single command line: install /boot/grub/stage1 d (fd0) /boot/grub/stage2 p /boot/grub/menu.lst 5b. If files "stage1" and "stage2" are stored elsewhere, e.g. in subdirectory "/foo", install GRUB on the second floppy disk like this (this is also a single command line): install=(fd0)/foo/stage1 (fd0) (fd0)/foo/stage2 0x8000 p (fd0)/foo/menu.lst Floppy disk #2 (the disk with the filesystem) is now bootable. xxx - Boot from disk #2, copy new/modified "stage2", and re-run "setup" or "install"? Will this work? (xxx - GRUB is not a shell -- it can't copy files, or list directories -- can it?) xxx - install syntax: 0x8000 This value gets embedded into the bootsector of the floppy to indicate the address that stage2 should be loaded into memory. p Modifies stage2, to report to the kernel the partition that stage 2 was found on (I think). (fd0)/boot/grub/menu.lst Modifies stage2, and tells it where to load the menu.lst (bootmenu) configuration file from. ================================================================ Making a Multiboot kernel ================================================================ Multiboot header ---------------- Whatever its file format, your kernel MUST have a Multiboot header. This header 1. must be aligned on a dword (4-byte) boundary, and 2. must appear in the first 8K of the kernel file. *** NOTE: An address within the first 8K of the .text section is not necessarily within 8K of the start of the file. ELF kernels ----------- GRUB understands the ELF file format directly. If your kernel is ELF, you can use the simple Multiboot header shown here: MULTIBOOT_PAGE_ALIGN equ 1http://www.multimania.com/placr/binutils.html (xxx - this server is often difficult to reach. Someone should mirror these tools. I'm near my disk quota :) I recommend building a regular COFF kernel, then doing this: objcopy-elf -O elf32-i386 krnl.cof krnl.elf Failing this, you can make GRUB load a COFF kernel by using the "aout kludge". This uses additional fields at the end of the Multiboot header, like this: MULTIBOOT_PAGE_ALIGN equ 1 ... int main(multiboot_info_t *boot_info) { if(boot_info->flags & 2) { kprintf("the command line is:\n'%s'\n", (char *)boot_info->cmdline); } ... xxx - more info ================================================================ Making a boot menu (file "menu.lst") ================================================================ Example 1: # Entry 0: title WildMagnolia root (fd0) kernel /boot/kernel.elf module /boot/mod_a module /boot/mod_b Example 2: # # Sample boot menu configuration file # # default - boot the first entry. default 0 # if have problem - boot the second entry. fallback 1 # after 30 sec boot default. timeout 30 # GNU Hurd title GNU/Hurd root (hd0,0) kernel /boot/gnumach.gz root=hd0s1 module /boot/serverboot.gz # Linux - boot ot second HDD title GNU/Linux kernel (hd1,0)/vmlinuz root=/dev/hdb1 # booting Mach - get kernel from floppy title Utah Mach4 multiboot root (hd0,2) pause Insert the diskette now
