ssbagpcmOS

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A minimal Linux-based operating system built from scratch using a custom kernel and BusyBox.

Features

• 🐧 Custom Linux kernel 6.19.8
• 📦 BusyBox-based userland with Alpine package manager (apk)
• 🌐 Networking with DHCP out of the box
• 💾 Live ISO boot (runs in RAM) or install to disk
• ⚡ KVM hardware acceleration support

Project Structure

.
├── iso_root/
│   ├── bzImage              # Linux kernel
│   ├── initramfs.cpio.gz    # Root filesystem (compressed)
│   ├── isolinux.bin         # ISOLINUX bootloader
│   ├── isolinux.cfg         # Bootloader configuration
│   └── ldlinux.c32          # SYSLINUX module
├── rootfs/                  # Root filesystem source (not shipped)
├── ssbagpcmOS.iso           # Bootable ISO image
└── README.md

Requirements

• qemu-system-x86_64 — Virtual machine emulator
• xorriso — ISO creation tool
• cpio — Archive tool for initramfs
• gzip — Compression

Install dependencies (Debian/Ubuntu)

sudo apt install qemu-system-x86 xorriso cpio gzip

Install dependencies (Arch Linux)

sudo pacman -S qemu-full xorriso cpio gzip

Quick Start

1. Boot the Live ISO

qemu-system-x86_64 \
  -enable-kvm \
  -cpu host \
  -cdrom ssbagpcmOS.iso \
  -nographic \
  -m 2048M \
  -netdev user,id=net0 -device virtio-net-pci,netdev=net0

Note: Remove -enable-kvm -cpu host if your system does not support KVM.

2. Exit QEMU

Press Ctrl+A then X to kill the VM.

Install to Disk

1. Create a virtual disk

qemu-img create -f qcow2 ssbagpcmOS-disk.qcow2 10G

2. Boot the ISO with the disk attached

qemu-system-x86_64 \
  -enable-kvm \
  -cpu host \
  -cdrom ssbagpcmOS.iso \
  -hda ssbagpcmOS-disk.qcow2 \
  -nographic \
  -m 2G \
  -netdev user,id=net0 -device virtio-net-pci,netdev=net0

3. Run the installer

sh /install.sh

The installer will automatically:

• Partition the disk
• Format the partitions
• Copy the system
• Install the bootloader
• Shutdown when done

4. Boot from disk (no ISO needed)

qemu-system-x86_64 \
  -enable-kvm \
  -cpu host \
  -hda ssbagpcmOS-disk.qcow2 \
  -nographic \
  -m 2G \
  -netdev user,id=net0 -device virtio-net-pci,netdev=net0

Building from Source

Rebuild the initramfs

If you modify the rootfs, rebuild the initramfs:

cd rootfs
find . | cpio -H newc -o | gzip > ../iso_root/initramfs.cpio.gz

Rebuild the ISO

xorriso -as mkisofs \
  -o ssbagpcmOS.iso \
  -b isolinux.bin \
  -c boot.cat \
  -no-emul-boot \
  -boot-load-size 4 \
  -boot-info-table \
  iso_root/

Full rebuild (initramfs + ISO)

cd rootfs
find . | cpio -H newc -o | gzip > ../iso_root/initramfs.cpio.gz
cd ..
xorriso -as mkisofs \
  -o ssbagpcmOS.iso \
  -b isolinux.bin \
  -c boot.cat \
  -no-emul-boot \
  -boot-load-size 4 \
  -boot-info-table \
  iso_root/

Commands Reference

Action	Command
Boot live ISO	qemu-system-x86_64 -enable-kvm -cpu host -cdrom ssbagpcmOS.iso -nographic -m 2048M -netdev user,id=net0 -device virtio-net-pci,netdev=net0
Create virtual disk	qemu-img create -f qcow2 ssbagpcmOS-disk.qcow2 10G
Boot ISO + disk	qemu-system-x86_64 -enable-kvm -cpu host -cdrom ssbagpcmOS.iso -hda ssbagpcmOS-disk.qcow2 -nographic -m 2G -netdev user,id=net0 -device virtio-net-pci,netdev=net0
Boot from disk	qemu-system-x86_64 -enable-kvm -cpu host -hda ssbagpcmOS-disk.qcow2 -nographic -m 2G -netdev user,id=net0 -device virtio-net-pci,netdev=net0
Rebuild initramfs	cd rootfs && find . | cpio -H newc -o | gzip > ../iso_root/initramfs.cpio.gz
Rebuild ISO	xorriso -as mkisofs -o ssbagpcmOS.iso -b isolinux.bin -c boot.cat -no-emul-boot -boot-load-size 4 -boot-info-table iso_root/
Exit QEMU	Ctrl+A then X