Replace bash with busybox for minimal footprint

Co-authored-by: johndoe6345789 <224850594+johndoe6345789@users.noreply.github.com>

ARCHITECTURE.md

@@ -26,7 +26,7 @@ Follows the Filesystem Hierarchy Standard (FHS):
 
 ```
 /
-├── bin/          Essential user binaries (bash, ls, cp, etc.)
+├── bin/          Essential user binaries (busybox with symlinks)
 ├── sbin/         System binaries (init, mount, etc.)
 ├── etc/          System configuration files
 ├── proc/         Kernel process information (virtual)
@@ -71,7 +71,7 @@ Init System (/sbin/init) [PID 1]
     ↓
 Mount filesystems
     ↓
-Spawn bash shell
+Spawn busybox sh shell
     ↓
 User interaction
 ```
@@ -91,11 +91,12 @@ User interaction
 - **Portability**: Works on any Linux system
 - **Reliability**: No missing library issues
 
-### Why Bash?
+### Why Busybox?
 
-- **Familiar**: Most users know bash
+- **Minimal**: Single binary provides dozens of utilities
-- **Powerful**: Full scripting capabilities
+- **Small footprint**: Typically <1MB for full feature set
-- **Standard**: Available on virtually all Linux systems
+- **Efficient**: Less memory and storage overhead than full GNU coreutils
+- **Standard**: De facto standard for embedded Linux systems
 
 ## Future Architecture
 
@@ -132,7 +133,7 @@ User interaction
 ## Performance
 
 - Fast boot time (seconds, not minutes)
-- Low memory footprint (~100MB base system)
+- Low memory footprint (~50MB base system with busybox)
 - No unnecessary background services
 - Efficient init system
 

CONTRIBUTING.md

@@ -39,7 +39,8 @@ SparkOS aims to be:
   - Comment complex logic
   
 - **Shell Scripts**: Follow Google Shell Style Guide
-  - Use `#!/bin/bash` shebang
+  - Use `#!/bin/sh` for POSIX-compliant scripts (preferred for busybox compatibility)
+  - Use `#!/bin/bash` only when bash-specific features are required
   - Quote variables
   - Use meaningful variable names
 

README.md

@@ -2,7 +2,7 @@
 
 A minimal Linux distribution designed for simplicity and portability. SparkOS features:
 
-- **Minimal footprint**: Barebones Linux system with bash shell
+- **Minimal footprint**: Barebones Linux system with busybox shell
 - **Portable**: dd-able disk image for USB flash drives
 - **Custom init**: Lightweight C init system
 - **Future-ready**: Designed to support Qt6/QML GUI and Wayland
@@ -12,7 +12,7 @@ A minimal Linux distribution designed for simplicity and portability. SparkOS fe
 
 The current MVP provides:
 - ✅ Custom init system written in C
-- ✅ Working bash shell environment
+- ✅ Working busybox shell environment
 - ✅ dd-able AMD64 image creation scripts
 - ✅ Minimal root filesystem structure
 - ✅ Build system (Makefile)
@@ -99,7 +99,7 @@ SparkOS/
 
 SparkOS uses a custom init system (`/sbin/init`) that:
 - Mounts essential filesystems (proc, sys, dev, tmp)
-- Spawns a bash login shell
+- Spawns a busybox sh login shell
 - Handles process reaping
 - Respawns shell on exit
 
@@ -138,14 +138,18 @@ make help
 To create a fully functional system, you need to populate the rootfs with binaries:
 
 ```bash
-# Example: Add bash (statically linked is best)
+# Example: Add busybox (statically linked is best)
-cp /bin/bash rootfs/bin/
+cp /bin/busybox rootfs/bin/
 
-# Example: Add essential utilities
+# Create busybox symlinks for common utilities
-cp /bin/{ls,cat,mkdir,rm,cp,mount} rootfs/bin/
+cd rootfs/bin
+for cmd in sh ls cat mkdir rm cp mount umount chmod chown ln; do
+    ln -sf busybox $cmd
+done
+cd ../..
 
-# Copy required libraries if not static
+# If using dynamically linked busybox, copy required libraries
-ldd rootfs/bin/bash  # Check dependencies
+ldd rootfs/bin/busybox  # Check dependencies
 # Copy libraries to rootfs/lib or rootfs/lib64
 ```
 
@@ -184,7 +188,7 @@ To create a fully bootable system, you'll also need:
 - Bootloader installation (handled by scripts)
 A single binary on top of Linux / Wayland that manages the OS, C++ CLI and Qt6/QML Full screen GUI. Android like design but more desktop orientated. A distribution that can be dd'ed to a USB flash drive. Root elevation powered by sudo. This project will need to set up a barebones distro (doesn't really need to be based on another, to keep things clean)
 
-MVP is just a to get to a bash prompt with sudo support. Install minimum on system, maybe even use busybox.
+MVP is just a to get to a shell prompt with sudo support. Install minimum on system using busybox for minimal footprint.
 
 We should try to build the system with github actions if possible.
 

config/build.conf

@@ -17,7 +17,7 @@ BOOTLOADER=syslinux
 INIT=sparkos-init
 
 # Default shell
-SHELL=/bin/bash
+SHELL=/bin/sh
 
 # Compiler flags
 CFLAGS=-Wall -O2 -static

rootfs/README.txt

@@ -14,5 +14,5 @@ Directory Structure:
   /home             - User home directories
 
 Note: This is a minimal system. You'll need to populate /bin and /usr/bin
-with actual binaries (bash, coreutils, etc.) from a proper Linux system
+with actual binaries (busybox, etc.) from a proper Linux system
 or by cross-compiling.

rootfs/etc/passwd

@@ -1 +1 @@
-root:x:0:0:root:/root:/bin/bash
+root:x:0:0:root:/root:/bin/sh

rootfs/root/.profile

@@ -1,10 +1,9 @@
-# SparkOS Root Bash Configuration
+# SparkOS Root Shell Configuration
 
 # Set prompt
 PS1='SparkOS:\w# '
 
 # Aliases
-alias ls='ls --color=auto'
 alias ll='ls -lah'
 alias ..='cd ..'
 

scripts/build.sh

@@ -28,9 +28,10 @@ echo ""
 echo "Build complete!"
 echo ""
 echo "Next steps to create a full bootable system:"
-echo "  1. Populate rootfs/bin with bash and essential utilities"
+echo "  1. Copy busybox to rootfs/bin/"
-echo "     (cp /bin/bash rootfs/bin/, etc.)"
+echo "     (cp /bin/busybox rootfs/bin/)"
-echo "  2. Copy required libraries to rootfs/usr/lib and rootfs/lib"
+echo "  2. Create symlinks in rootfs/bin for common utilities"
+echo "     (cd rootfs/bin && for cmd in sh ls cat mkdir rm cp mount; do ln -sf busybox \$cmd; done)"
 echo "  3. Add a Linux kernel to rootfs/boot/vmlinuz"
 echo "  4. Run: sudo make image"
 echo ""

scripts/setup_rootfs.sh

@@ -1,6 +1,6 @@
 #!/bin/bash
 # SparkOS Setup Script
-# Sets up a minimal rootfs with bash and essential utilities
+# Sets up a minimal rootfs with busybox and essential utilities
 
 set -e
 
@@ -37,7 +37,7 @@ EOF
 
 # /etc/passwd
 cat > "$ROOTFS_DIR/etc/passwd" << 'EOF'
-root:x:0:0:root:/root:/bin/bash
+root:x:0:0:root:/root:/bin/sh
 EOF
 
 # /etc/group
@@ -69,15 +69,14 @@ echo "Type 'help' for available commands"
 echo ""
 EOF
 
-# Create .bashrc for root
+# Create .profile for root (busybox uses .profile instead of .bashrc)
-cat > "$ROOTFS_DIR/root/.bashrc" << 'EOF'
+cat > "$ROOTFS_DIR/root/.profile" << 'EOF'
-# SparkOS Root Bash Configuration
+# SparkOS Root Shell Configuration
 
 # Set prompt
 PS1='SparkOS:\w# '
 
 # Aliases
-alias ls='ls --color=auto'
 alias ll='ls -lah'
 alias ..='cd ..'
 
@@ -131,7 +130,7 @@ Directory Structure:
   /home             - User home directories
 
 Note: This is a minimal system. You'll need to populate /bin and /usr/bin
-with actual binaries (bash, coreutils, etc.) from a proper Linux system
+with actual binaries (busybox, etc.) from a proper Linux system
 or by cross-compiling.
 EOF
 
@@ -141,8 +140,8 @@ echo ""
 echo "Next steps:"
 echo "  1. Build init: make init"
 echo "  2. Install init: make install"
-echo "  3. Copy bash and essential binaries to rootfs/bin/"
+echo "  3. Copy busybox to rootfs/bin/ and create symlinks"
 echo "  4. Create bootable image: sudo make image"
 echo ""
-echo "Note: You'll need to populate the rootfs with actual binaries"
+echo "Note: You'll need to populate the rootfs with busybox binary"
 echo "      before creating a bootable image."

src/init.c

@@ -29,7 +29,7 @@ static void spawn_shell() {
     
     if (pid == 0) {
         // Child process - exec shell
-        char *argv[] = {"/bin/bash", "--login", NULL};
+        char *argv[] = {"/bin/sh", "-l", NULL};
         char *envp[] = {
             "HOME=/root",
             "PATH=/bin:/sbin:/usr/bin:/usr/sbin",
@@ -38,11 +38,7 @@ static void spawn_shell() {
             NULL
         };
         
-        execve("/bin/bash", argv, envp);
+        execve("/bin/sh", argv, envp);
-        
-        // If bash fails, try sh
-        char *sh_argv[] = {"/bin/sh", NULL};
-        execve("/bin/sh", sh_argv, envp);
         
         perror("failed to exec shell");
         exit(1);