Merge pull request #1 from jetrails/boot-hooks

Add boot hooks doc

Author: null93

docs/guides/custom-boot-hooks/index.md

@@ -0,0 +1,118 @@
+---
+title: Add Custom Boot Hook to /mnt/jrc-comms/hooks/boot.d
+---
+
+This guide explains how to add a custom boot hook to `/mnt/jrc-comms/hooks/boot.d/` in applications that execute scripts in numerical order. Follow these steps to ensure proper execution order and functionality.
+
+!!! Assumption:
+We assume you have root access to modify files in `/mnt/jrc-comms/hooks/boot.d/`.
+!!!
+
+## Create Custom Boot Hook
+
+### 1. Create Your Script  
+Create a new shell script with a filename starting with `99-` (to ensure it runs last). For example:  
+
+```bash
+#!/bin/bash
+/mnt/jrc-comms/hooks/boot.d/99-custom-task
+
+echo "Running custom boot task..."
+```
+
+### 2. Set Permissions and Ownership  
+Make the script executable and ensure it’s owned by `root`:  
+
+```bash
+sudo chown root:root /mnt/jrc-comms/hooks/boot.d/99-custom-task
+sudo chmod +x /mnt/jrc-comms/hooks/boot.d/99-custom-task
+```
+
+### 3. Verify Execution Order  
+The application runs scripts in ascending order based on their numeric prefixes. Scripts added to `/mnt/jrc-comms/hooks/boot.d` will be injected into `/opt/jrc/hooks/boot.d` based on script prefix automatically. For example:  
+
+- `05-mount-recovery-mount` runs first (found in `/opt/jrc/hooks/boot.d`)
+- `10-cluster-clean` runs next (found in `/opt/jrc/hooks/boot.d`)
+- `99-custom-task` runs last (added to `/mnt/jrc-comms/hooks/boot.d`)
+
+**Key rules:**  
+- Prefixes determine execution order (e.g., `00-` to `99-`)  
+- Use two-digit numbering for clarity (e.g., `05-`, `10-`, `99-`)  
+- Scripts with the same prefix may execute in lexicographical order, but avoid ambiguity by using unique prefixes  
+- Scripts added to `/mnt/jrc-comms/hooks/boot.d` will persist AMI upgrades, stack clones, etc.
+
+---
+
+## Example Walkthrough  
+To log system time at the end of the boot process:  
+
+```bash
+#!/bin/bash
+/mnt/jrc-comms/hooks/boot.d/99-custom-task
+
+LOGFILE="/var/log/custom-boot.log"
+echo "Boot completed at: $(date)" >> $LOGFILE
+```
+
+---
+
+## Troubleshooting Tips  
+1. **Test your script manually** before relying on the boot process: 
+
+```bash
+sudo /mnt/jrc-comms/hooks/boot.d/99-custom-task
+```
+
+2. **Check logs** for errors (e.g., `/var/log/syslog` or `journalctl`)  
+
+3. **Validate script syntax** using:  
+
+```bash
+bash -n /mnt/jrc-comms/hooks/boot.d/99-custom-task
+```
+
+By following this structure, you can extend the boot process with custom logic while maintaining predictable execution order.
+
+---
+
+### Alternative to fstab Mounting Using Boot Hook Script
+
+AutoPilot's boot hook system provides a more reliable alternative to `/etc/fstab` for bind mounts within dynamic environments, particularly when dealing with paths that might not be available during early boot stages.
+
+The following is an example of how you would implement a boot hook script to create hard links. Typically this would be accomplished within `/etc/fstab`.
+
+## Boot Hook Script Implementation
+
+### 1. Create /mnt/jrc-comms/hooks/boot.d/99-links Script
+
+Creates bind mounts after filesystems are available
+
+```bash
+#!/bin/bash
+/mnt/jrc-comms/hooks/boot.d/99-links
+
+echo "Creating bind mounts..."
+mount --bind /var/www/domain.com/shared/var/salesexport /home/user/salesexport
+mount --bind /var/www/domain.com/shared/media/importexport /home/user/importexport
+```
+
+### 2. Set Permissions
+
+```bash
+sudo chmod +x /mnt/jrc-comms/hooks/boot.d/99-links
+sudo chown root:root /mnt/jrc-comms/hooks/boot.d/99-links
+```
+
+## Verification
+1. **Validate script syntax**:
+
+```bash
+bash -n /mnt/jrc-comms/hooks/boot.d/99-custom-task
+```
+
+2. **Check active mounts**:
+
+```bash
+mount | grep bind
+```
+