Buildroot for 486

Here are the steps I used in order to get a brand new Linux version 4 kernel running on an old 486 DX computer. The setup is based on the Buildroot system for making embedded systems. The end result is the kernel with a very simple BusyBox based userland.

All the steps are based on the 2015.05 version of Buildroot, gotten from http://buildroot.uclibc.org/downloads/buildroot-2015.05.tar.gz

Get the three necessary configuration files from Here.

First of all copy the configuration files into Buildroot and prepare it:

mkdir board/i486
cp i486_defconfig configs/
cp linux-4.0.4-i486.defconfig board/i486
cp extlinux.conf board/i486
make i486_defconfig
          

For any further changes to the configuration, use:

make menuconfig
make linux-menuconfig
          

Then build!:

make
          

I had to use extlinux as a bootloader, since neither syslinux nor GRUB worked correctly in my case. A Compact Flash card was inserted as /dev/sdd, and setup like this:

fdisk /dev/sdd # One primary partition, active, uses all space.
sudo cat /usr/share/syslinux/mbr.bin > /dev/sdd
mkfs.ext2 /dev/sdd1
          

Once the CF card is prepared, relative from the Buildroot folder, the files can be copied over:

mount /mnt/sdd1
sudo tar xf ./output/images/rootfs.tar -C /mnt/sdd1
sudo mkdir /mnt/sdd1/boot
sudo cp ./output/images/bzImage /mnt/sdd1/boot/
sudo cp ./board/i486/extlinux.conf /mnt/sdd1/boot/
sudo extlinux -i /mnt/sdd1/boot
sync
umount /mnt/sdd1
          

The card is then ready to be used.