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🚀 Early Boot Script (boot.sh)

MOS provides an Early Boot Script that is executed at the very beginning of the boot process.

This script runs before any drivers are loaded, before networking, before storage pools, and before all services. At this stage, only the root filesystem (rootfs) is available.

This script is intended for deep system-level modifications and should be used with extreme care.

📍 Script Location​

/boot/optional/scripts/boot.sh

If this file exists, MOS will execute it automatically during early boot.

⏱️ Execution Order​

The Early Boot Script is executed in the following phase:

  1. Kernel and init process start
  2. Early Boot Script is executed
  3. Drivers are loaded
  4. Network is initialized
  5. Storage pools are mounted
  6. Services are started

This is the earliest execution point available in MOS.

⚠️ Environment Limitations​

At this stage of the boot process:

  • No drivers are loaded
  • No network is available
  • No storage pools are mounted
  • No services are running
  • Environment variables are minimal or unavailable

Only the root filesystem is accessible.

🔧 Command Usage Requirements​

Because the environment is extremely limited:

  • Always use full paths to binaries
  • Do not rely on $PATH

Examples:

/usr/bin/echo "Early boot"
/bin/mount
/sbin/modprobe

Using commands without full paths (e.g. echo, mount) may fail.

🔧 Typical Use Cases​

  • Very early system initialization
  • Low-level system preparation
  • Hardware workarounds required before driver load
  • Kernel or init-related adjustments
  • System behavior changes that must occur before everything else

🧭 Recommended Usage​

This script should be used only when absolutely necessary.

For most use cases, prefer:

  • Pre-Start Scripts (before pools and services)
  • Pool Mount Scripts (after a specific pool is mounted)
  • Post-Start Scripts (after full startup)
  • Cron jobs (for standard automation)

The Early Boot Script is a last-resort tool for deep system intervention.

📌 Script Execution Notes​

  • The script does not need to be executable
  • No chmod +x is required
  • Script execution is handled internally by MOS

The mere existence of the file at the defined path is sufficient.

🚨 Critical Warnings​

  • Errors can prevent the system from booting
  • Debugging is difficult at this stage
  • Logging is extremely limited
  • Incorrect commands may require recovery access
warning

Use this script only if you fully understand the MOS boot process and Linux system initialization.

✅ Summary​

  • Executed at the earliest possible boot stage
  • Runs before drivers, networking, pools, and services
  • Only rootfs is available
  • Requires full paths to all commands
  • Intended for deep system-level customization
  • Located under Advanced-Usage for a reason