QEMU Build Tutorial
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If you don't have a mainboard supported by LinuxBIOS don't worry: Qemu can help you to emulate one.
This nice tutorial was written by Alan Carvalho de Assis <email@example.com>, with additions by Ed Swierk <firstname.lastname@example.org>.
While there are many ways to use LinuxBIOS to load and run a Linux kernel, this tutorial covers two of the most common:
- LinuxBIOS with FILO as payload, using FILO to load a Linux kernel and initramfs from a hard disk image.
- LinuxBIOS with a Linux kernel and initramfs as payload.
You need the following software packages:
- LinuxBIOSv2 r2405 or greater
- Qemu 0.8.2 or greater
- FILO 0.4.2 or greater (if using FILO)
- mkelfImage 2.7 or greater (if not using FILO)
plus a Linux kernel and root filesystem and a working development environment (make, gcc, etc.). gcc 4.0.x and 4.1.x are known to work.
Download FILO (I used filo-0.4.2.tar.bz2), decompress it, enter inside directory created.
First invocation of make creates the default Config file.
Edit this file as you like. The default configuration worked to me.
$ vi Config
Run make again to create filo.elf, the ELF FILO image.
You will need this file (filo.elf) to start Linux. This is used as a payload in LinuxBIOS, when executed it can load Linux kernel.
Download LinuxBIOS source code (I used LinuxBIOSv2-2394). Decompress it.
Change to directory targets/emulation/qemu-i386 and modify Config.lb to point to your filo.elf.
Return to targets directory and execute:
$ ./buildtarget emulation/qemu-i386
Go to targets/emulation/qemu-i386/qemu-i386 and execute:
It will create the file "qemu-bios.rom"
Rename this file to "bios.bin" and copy to your HOME directory.
Creating your disk image
Create a empty file (~ 200MB):
# dd if=/dev/zero of=disk.img bs=1M count=200
Format it as ext2:
# mkfs.ext2 -F disk.img
Mount it on somewhere:
# mount disk.img /mnt/rootfs -t ext2 -o loop
Now you need copy a root filesystem to it.
I create a directory /debian and used debootstrap command to create a basic root filesystem, but you can use any root filesystem from your distro (i.e. copy one from diskboot.img):
# cp -R /debian/* /mnt/rootfs
Open the file /mnt/rootfs/etc/inittab and change runlevel to level 1:
Change to /mnt/rootfs/boot and copy your default vmlinuz and initrd:
# cp /boot/vmlinuz-2.6.16-2-686 vmlinuz # cp /boot/initrd.img-2.6.16-2-686 initrd
Change to /root and umount /mnt/rootfs:
# umount /mnt/rootfs
Exit of root account:
Starting LinuxBIOS in Qemu
Execute Qemu using the followings parameters:
$ qemu -L ~ -hda disk.img -nographic -no-kqemu -d in_asm,exec
When appear "boot:" text enter it:
boot: hda:/boot/vmlinuz root=/dev/hda initrd=/boot/initrd console=tty0 console=ttyS0,115200