Replace bash with busybox for minimal footprint

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

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 ..'