feat: add redundant root with EFI mirror setup guide

Covers disk formatting, BTRFS RAID1 conversion, fstab configuration,
and the update-efi-mirror script with apt post-install hook setup.
Includes a separate procedure for migrating to a new disk.

README.md

@@ -10,6 +10,7 @@ This repository is structured into several key directories:
   - `scripts/library/`: Libraries used by Python scripts.
     - `venv_utils.py`: Utility functions for creating, activating, and managing Python virtual environments.
   - `change_case.py`: A script for renaming files and directories by changing their case.
+  - `update-efi-mirror.sh`: Script for syncing a two drive EFI mirror.
   - `video_autoreduce.py`: A script for automatic resolution reduction of video files.
   - `video_autoreduce_rename.py`: A script for automated renaming of video files post resolution reduction.
   - `video_manage_audio.py`: A script for removing audio from video files.
@@ -27,6 +28,7 @@ This repository is structured into several key directories:
   - `pip-packaging.md`: Packaging and publishing Python projects with pip.
   - `ssh.md`: SSH configuration, key management, and tunneling tips.
   - `storage.md`: Storage tooling — smartctl, badblocks, dd, hdparm, fdisk, and fstab/mount management.
+  - `update-efi-mirror.md`: Redundant root with EFI mirror setup guide.
   - `wordpress.md`: WordPress debugging and tips.
 
 - **pages/other/**: Templates for other pages, such as the homepage of my Debian package repository. These are provided as inspiration and should not be used as-is.
@@ -40,6 +42,7 @@ This repository is structured into several key directories:
 
 - **setups/**: A collection of markdown files containing notes on configuring servers, including:
   - `debian_setup_aptly.md`: Comprehensive guide for installing Aptly on Debian.
+  - `debian_setup_dolibarr.md`: Comprehensive guide for installing Dolibarr on Debian.
   - `debian_setup_gitea.md`: Comprehensive guide for installing Gitea on Debian.
 
 ## 📖 Documentation

notes/update-efi-mirror.md

@@ -0,0 +1,334 @@
+# Redundant Root with EFI Mirror
+
+## Table of Contents
+
+- [Redundant Root with EFI Mirror](#redundant-root-with-efi-mirror)
+  - [Table of Contents](#table-of-contents)
+  - [Overview](#overview)
+  - [Placeholders](#placeholders)
+  - [How It Works](#how-it-works)
+  - [Paths](#paths)
+  - [Setup Procedure](#setup-procedure)
+    - [1. Format the Disks](#1-format-the-disks)
+    - [2. Convert the Root Filesystem to BTRFS RAID1](#2-convert-the-root-filesystem-to-btrfs-raid1)
+    - [3. Configure fstab](#3-configure-fstab)
+    - [4. Install the Sync Script](#4-install-the-sync-script)
+    - [5. Configure apt to Run the Script Post-Install](#5-configure-apt-to-run-the-script-post-install)
+    - [6. Test](#6-test)
+  - [Moving to a New Disk](#moving-to-a-new-disk)
+
+## Overview
+
+This setup provides a redundant Debian root drive using BTRFS RAID1 across two disks, with a synced EFI partition on both so the machine can boot from either. The script `update-efi-mirror` keeps the backup EFI in sync and re-installs GRUB on both physical disks. It is triggered automatically after every `apt` operation.
+
+## Placeholders
+
+Replace the placeholders below with the appropriate values for your setup:
+
+- **Devices**
+  - Primary disk: `<primary-disk>` (e.g., /dev/sda, /dev/nvme0n1)
+  - Backup disk: `<backup-disk>` (e.g., /dev/sdb, /dev/nvme1n1)
+  - Primary EFI partition: `<primary-efi-part>` (e.g., /dev/sda1, /dev/nvme0n1p1)
+  - Backup EFI partition: `<backup-efi-part>` (e.g., /dev/sdb1, /dev/nvme1n1p1)
+  - Primary root partition: `<primary-root-part>` (e.g., /dev/sda2, /dev/nvme0n1p2)
+  - Backup root partition: `<backup-root-part>` (e.g., /dev/sdb2, /dev/nvme1n1p2)
+  - Primary swap partition: `<primary-swap-part>` (e.g., /dev/sda3, /dev/nvme0n1p3)
+  - Backup swap partition: `<backup-swap-part>` (e.g., /dev/sdb3, /dev/nvme1n1p3)
+
+- **UUIDs**
+  - Primary EFI UUID: `<primary-efi-uuid>` (e.g., D167-0F46)
+  - Backup EFI UUID: `<backup-efi-uuid>` (e.g., 08E8-A87C)
+  - Root BTRFS UUID: `<root-uuid>` (e.g., 387526ec-f3bd-4fa8-a17e-e985121ada0b)
+  - Primary swap UUID: `<primary-swap-uuid>`
+  - Backup swap UUID: `<backup-swap-uuid>`
+
+## How It Works
+
+- The root filesystem is BTRFS RAID1 across two partitions. Either disk alone can serve reads and writes.
+- Each disk has its own EFI partition. GRUB is installed on both physical disks.
+- After every `apt` install or upgrade, an apt hook calls `update-efi-mirror`, which:
+  1. Rsyncs the live `/boot/efi` to the backup EFI partition.
+  2. Runs `grub-install` on both physical disks.
+- Either disk can be removed and the system will still boot and run.
+
+## Paths
+
+- **Sync script**: `/usr/local/sbin/update-efi-mirror`
+- **Apt hook**: `/etc/apt/apt.conf.d/99-update-efi-mirror`
+- **fstab**: `/etc/fstab`
+
+## Setup Procedure
+
+### 1. Format the Disks
+
+**Verify which disks are present before touching anything**
+
+```bash
+lsblk
+lsblk -f
+```
+
+**Open `fdisk` on the backup disk**
+
+If the disk was previously used at a smaller capacity, the GPT backup table may be misaligned — `fdisk` will correct it on write.
+
+```bash
+fdisk <backup-disk>
+```
+
+Create a GPT partition table if not already present:
+
+```
+g
+```
+
+**Check the primary disk partition layout and note the exact sector boundaries**
+
+```bash
+fdisk -l <primary-disk>
+```
+
+This shows the `Start` and `End` sectors for each partition. Use these values when partitioning the backup disk so the layouts match exactly.
+
+**Create the three partitions to match the layout of the primary disk**
+
+| #   | Size      | Type       |
+| --- | --------- | ---------- |
+| 1   | 830M      | EFI System |
+| 2   | ~12G      | Linux fs   |
+| 3   | Remainder | Linux swap |
+
+Inside `fdisk`, the sequence is:
+
+```
+n          # new partition
+            # enter the exact End sector from the primary disk to match partition sizes
+t          # change type
+1          # select partition 1
+EFI System # set type to EFI
+t          # change type
+3          # select partition 3
+Linux swap # set type to swap
+w          # write and exit
+```
+
+**Partition sizes must be at least as large as the corresponding primary partition** — the BTRFS replace will fail if the target partition is smaller than the source.
+
+**Format the new EFI partition**
+
+```bash
+apt install dosfstools   # if not installed
+mkfs.fat -F32 <backup-efi-part>
+```
+
+**Format the new swap partition**
+
+```bash
+mkswap <backup-swap-part>
+```
+
+**Check UUIDs of the new partitions**
+
+```bash
+lsblk -f <backup-disk>
+```
+
+### 2. Convert the Root Filesystem to BTRFS RAID1
+
+**Add the backup partition to the BTRFS volume**
+
+```bash
+btrfs device add <backup-root-part> /
+```
+
+**Convert to RAID1**
+
+```bash
+btrfs balance start -mconvert=raid1 -dconvert=raid1 /
+```
+
+Monitor the balance:
+
+```bash
+btrfs balance status /
+```
+
+**Verify the final layout**
+
+```bash
+btrfs filesystem show /
+btrfs fi usage /
+```
+
+### 3. Configure fstab
+
+Edit `/etc/fstab` to mount the primary EFI partition normally and document the backup EFI UUID in a commented-out entry. The script reads the backup UUID from this comment.
+
+**Edit fstab**
+
+```bash
+nano /etc/fstab
+```
+
+The fstab should contain:
+
+```
+# Primary EFI — mounted at boot
+UUID=<primary-efi-uuid>  /boot/efi  vfat  umask=0077  0  1
+
+# Backup EFI — not auto-mounted, used by update-efi-mirror
+#UUID=<backup-efi-uuid> /boot/efi vfat umask=0077 0 1
+
+# Root — BTRFS RAID1 (both partitions share the same UUID)
+UUID=<root-uuid>  /  btrfs  defaults,noatime  0  1
+
+# Swap — both disks
+UUID=<primary-swap-uuid>  none  swap  sw  0  0
+UUID=<backup-swap-uuid>   none  swap  sw  0  0
+```
+
+The backup EFI line must start with `#UUID=` — this is the format the script greps for:
+
+```bash
+grep "^#UUID=" /etc/fstab | grep "/boot/efi"
+```
+
+**Reload systemd after editing fstab**
+
+```bash
+systemctl daemon-reload
+```
+
+### 4. Install the Sync Script
+
+**Create the script**
+
+```bash
+nano /usr/local/sbin/update-efi-mirror
+```
+
+Paste the contents of `update-efi-mirror.sh`.
+
+**Set ownership and permissions**
+
+```bash
+chown root:root /usr/local/sbin/update-efi-mirror
+chmod 755 /usr/local/sbin/update-efi-mirror
+```
+
+The script will:
+
+1. Detect the currently mounted EFI partition and its disk.
+2. Read the backup EFI UUID from the `#UUID=` comment in `/etc/fstab`.
+3. Mount the backup EFI to a temp directory, rsync all files from the live EFI, then unmount.
+4. Run `grub-install --recheck` on both physical disks.
+
+### 5. Configure apt to Run the Script Post-Install
+
+**Create the apt hook**
+
+```bash
+nano /etc/apt/apt.conf.d/99-update-efi-mirror
+```
+
+Add:
+
+```
+DPkg::Post-Invoke {"if [ -x /usr/local/sbin/update-efi-mirror ]; then /usr/local/sbin/update-efi-mirror; fi";};
+```
+
+This runs the sync script after every `apt` operation that invokes `dpkg` — including kernel upgrades, which update `/boot/efi` with new initramfs and GRUB config.
+
+### 6. Test
+
+**Run the script manually**
+
+```bash
+/usr/local/sbin/update-efi-mirror
+```
+
+Expected output:
+
+```
+Syncing EFI files: <primary-efi-uuid> -> <backup-efi-uuid>
+EFI Files Sync Complete.
+Updating GRUB bootloader on both physical disks...
+Redundancy Complete: Files synced and GRUB updated on <primary-disk> and <backup-disk>.
+```
+
+**Test the apt hook**
+
+```bash
+apt update
+apt upgrade -y
+```
+
+The sync output should appear at the end of the upgrade, after GRUB regenerates its config.
+
+**Verify the backup EFI contents match**
+
+```bash
+TMPMNT=$(mktemp -d)
+mount -U <backup-efi-uuid> "$TMPMNT"
+diff -r /boot/efi/ "$TMPMNT/"
+umount "$TMPMNT"
+rmdir "$TMPMNT"
+```
+
+**Verify GRUB is installed on both disks**
+
+```bash
+fdisk -l <primary-disk> | grep -i efi
+fdisk -l <backup-disk>  | grep -i efi
+```
+
+**`Optional` Boot from the backup disk**
+
+Swap the boot order in BIOS/UEFI to confirm the machine boots cleanly from `<backup-disk>`.
+
+## Moving to a New Disk
+
+Use this procedure when replacing one of the two disks in the BTRFS RAID1 — for example when upgrading to a larger drive.
+
+**1. Partition the new disk** following [Step 1](#1-format-the-disks).
+
+**2. Find the device ID of the partition to be replaced:**
+
+```bash
+btrfs filesystem show /
+```
+
+**3. Shrink the filesystem on the disk being replaced to fit the new partition:**
+
+```bash
+btrfs filesystem resize <device-id>:<size> /
+```
+
+**4. Replace the old partition with the new one:**
+
+```bash
+btrfs replace start <device-id> <new-root-part> /
+btrfs replace status /
+```
+
+**5. Grow the new partition to max:**
+
+```bash
+btrfs filesystem resize <device-id>:max /
+```
+
+**6. Update fstab** if the backup EFI UUID has changed (new disk = new EFI UUID):
+
+```bash
+lsblk -f <new-disk>
+nano /etc/fstab
+systemctl daemon-reload
+```
+
+**7. Run the sync script** to install GRUB on the new disk and populate its EFI partition:
+
+```bash
+/usr/local/sbin/update-efi-mirror
+```
+
+**8. Verify** following [Step 6](#6-test).