Setting the boot order of your Proxmox VE server is crucial to system stability and disaster recovery! 🔧 Setting it incorrectly can lead to boot failure or data loss. This guide will walk you through every step of the way. — ### 🔍 Why is setting the boot order important? 1. Multi-disk environment – Specifying the correct boot disk is essential when configuring ZFS mirroring or RAID. – Example: When mirroring sda (SSD) and sdb (HDD), set SSD as the first boot device. 2. Failure tolerance – Automatically boot from the backup disk in case the primary disk fails. 3. Performance optimization – Shorten startup time by setting SSD as the first boot device. — ### ⚙️ Method 1: Set in BIOS/UEFI (most basic) ✅ Step-by-step: 1. Power on the server → Press DEL/F2/F10 keys repeatedly (varies by motherboard) 2. Enter Boot Menu (usually F8/F12) Example screen: [ ] USB Drive [x] SSD (sda) [ ] HDD (sdb) [ ] PXE Network 3. Select disk with ↑/↓ keys → +/- Change the order with key 4. F10 Save and Reboot ⚠️ Note: – If in UEFI mode, debian may be displayed instead of Proxmox – Disabling CSM (compatibility mode) recommended (for UEFI booting) — ### 🐧 Method 2: Configuring GRUB in Proxmox (Advanced) GRUB (GRand Unified Bootloader) is the bootloader in Linux that controls kernel selection. #### Step 1: Open the GRUB config file bash nano /etc/default/grub #### Step 2: Add boot order options bash GRUB_DEFAULT="0" # Boot the first entry by default GRUB_TIMEOUT=5 # Show menu for 5 seconds GRUB_DISABLE_OS_PROBER=false # Enable foreign OS detection #### Step 3: Force disk priority (example) bash # Boot a specific disk first (e.g. sda) GRUB_CMDLINE_LINUX_DEFAULT="root=/dev/sda2" #### Step 4: Apply changes bash update-grub # Apply settings reboot # Reboot — ### 🔄 Method 3: Setting boot device priority in a ZFS pool Configure ZFS mirroring to automatically fall back to sdb in the event of a primary disk (sda) failure: 1. Current boot pool state Check bash zpool status -b Example output: pool: rpool state: ONLINE config: NAME STATE mirror-0 ONLINE sda3 ONLINE 👈 Current booting disk sdb3 ONLINE 2. Change boot priority bash zpool set bootpath=/dev/disk/by-id/ata-SSD-sdb rpool 3. Confirm changes bash zpool get bootpath rpool — ### 🚨 Troubleshooting tips 1. How to recover from boot failure – Boot with Proxmox installation USB → Select Rescue Boot mode – Run grub-install /dev/sda 2. Frequent errors – “disk 'hd0' not found”: GRUB fails to recognize the disk → Re-run grub-mkconfig – UEFI boot failure: Check ESP(EFI System Partition) → Add entry with efibootmgr -v 3. Collection of essential commands bash efibootmgr -v # Check UEFI boot entries lsblk -o NAME,MOUNTPOINT # Check disk structure proxmox-boot-tool status # Check Proxmox bootloader status — ### 💡 Optimal boot configuration strategy 1. Apply the 3-2-1 principle – Primary boot disk (SSD) + Mirroring (HDD) + External backup (USB) 2. Periodic inspection bash # Check the boot disk SMART status every month smartctl -a /dev/sda | grep "Reallocated_Sector_Ct" 3. Example of automatic recovery script bash # Switch to sdb in case of primary disk (sda) error if [ $(zpool status rpool | grep sda | grep -c "DEGRADED") -gt 0 ]; then zpool set bootpath=/dev/sdb rpool reboot fi — > 📌 Key takeaways: > 1. Single disk: BIOS/UEFI settings is sufficient > 2. ZFS mirroring: zpool set bootpath must be applied > 3. If custom kernel is needed: Edit GRUB settings > 4. Periodically run proxmox-boot-tool refresh to update the bootloader Your server should now reliably boot from the desired disk**! 💻⚡ Be sure to test with reboot after configuring. If you encounter any issues, please leave a comment with your questions! D
