Initial commit

env.sh

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+#!/usr/bin/env bash
+export BD="$(dirname "$(realpath -s "$BASH_SOURCE")")"
+export PATH="$BD/path:$PATH"

path/get-deps

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+#!/usr/bin/env bash
+sudo apt install git build-essential flex bison libncurses-dev qemu-system-x86 syslinux

path/make-initrd

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+#!/usr/bin/env bash
+set -e
+cd "$BD"
+bbver="1.33.1"
+mkdir -p initrd
+cd initrd
+wget "https://busybox.net/downloads/busybox-$bbver.tar.bz2"
+tar -xvf "busybox-$bbver.tar.bz2"
+cd "busybox-$bbver"
+make allnoconfig
+
+make menuconfig
+#    Settings > Build static binary (no shared libs)
+#    Coreutils > chroot, sleep, mkdir
+#    Linux Module Utilities > modprobe
+#    Linux System Utilities > switch_root
+#    Shells > ash, Optimize for size instead of speed
+
+make
+make install
+mkdir -p ../fs
+mv _install/. ../fs
+cd ../fs
+mkdir -p "proc" "sys" "lib/modules"
+#sudo mknod -m 644 "dev/console" c 5 1
+#sudo mknod -m 644 "dev/null" c 1 3
+
+echo '#!/bin/sh
+mkdir -p /proc /sys /mnt/root
+mount -t proc none /proc
+mount -t sysfs none /sys
+modprobe ata_generic
+modprobe vfat
+sleep 5
+mount "/sys/dev/block/8:1" /mnt/root
+exec switch_root /mnt/root /sbin/init
+' >"bin/init"
+chmod +x "bin/init"
+find . | cpio -H newc -o | gzip -9 > ../rootfs.cpio.gz # use XZ instead?

path/make-linux

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+#!/usr/bin/env bash
+set -e
+cd "$BD"
+git clone --depth=1 https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
+cd linux
+make tinyconfig
+
+make menuconfig
+#    General Setup > Initial RAM filesystem and RAM disk (initramfs/initrd)
+#    General Setup > Configure standard kernel features (expert users) > Enable support for printk
+#    Processor type and features > Processor family > 486
+#    Device Drivers > Character devices > Enable TTY
+#    Executable file formats > Kernel support for ELF binaries
+#    Executable file formats > Kernel support for scripts starting with #!
+# CONFIG_ATA_GENERIC
+
+make bzImage
+mv arch/x86/boot/bzImage .