🛠 Déplacer le rootfs sur un SSD NVMe via le port mini-PCIe

Objectives

The mini-PCIe port on the BPI-CM4IO is wired for PCIe Gen2 x1 + USB 2.0: with a mini-PCIe to NVMe adapter (the carrier board does not have an M.2 M-key connector), the vendor wiki measures 351 MB/s read speed and 101 k IOPS at 4k random. Absolute constraint: the A311D ROM and the u-boot BSP do not support booting over PCIe — the bootloader must remain on the SD card (or eMMC), and only the rootfs is moved to the SSD, via setenv rootfsdev in /boot/boot.ini.

Hardware

• BPI-CM4 + BPI-CM4IO, vendor image (procedure documented in the wiki) or Armbian
• Mini-PCIe to NVMe adapter + SSD (e.g., Samsung 970 EVO Plus to reproduce the wiki figures)
• 5 V / 3 A power supply (the SSD adds to the power consumption)
• A system that already boots from microSD

Complete code

# 1) Carrier éteint : visser l'adaptateur + SSD dans le port mini-PCIe, rallumer.
sudo apt install -y nvme-cli rsync
lsblk && sudo nvme list          # le SSD apparaît comme /dev/nvme0n1

# 2) Partitionner (p1 boot, p2 racine ext4) et formater
sudo fdisk /dev/nvme0n1
sudo mkfs.ext4 /dev/nvme0n1p2

# 3) Copier le système en cours sur le SSD
sudo mkdir -p /mnt/nvme && sudo mount /dev/nvme0n1p2 /mnt/nvme
sudo rsync -aAXx --exclude=/proc --exclude=/sys --exclude=/dev --exclude=/tmp / /mnt/nvme/

# 4) Forcer la racine sur le SSD (partition boot de la SD)
sudo mount /dev/mmcblk1p1 /mnt
sudo tee -a /mnt/boot.ini >/dev/null <<'EOF'
setenv rootfsdev "/dev/nvme0n1p2"
EOF
# Si la SD et le PCIe se marchent dessus : sortir la SD du mode UHS
sudo sed -i 's/^user_kernel_args=.*/user_kernel_args=pci=pcie_bus_safe disableuhs/' /mnt/env.txt
sudo umount /mnt /mnt/nvme && sudo reboot

# 5) Vérifier et benchmarker
findmnt -no SOURCE /             # -> /dev/nvme0n1p2
sudo hdparm -Tt /dev/nvme0n1p2

Expected verification

findmnt / returns /dev/nvme0n1p2; hdparm approaches the 350 MB/s published by the wiki; the PiBenchmarks Storage score jumps (24550 versus 5446 on eMMC). The system must continue to request the SD card (or eMMC) at startup: this is normal, as it is the only boot path for the platform.

Common errors

• Removing the microSD card "since it boots from the SSD": without a bootloader on SD/eMMC, there is no boot at all.
• Looking for an M.2 port: it does not exist on either the module or the carrier board; only the mini-PCIe format is provided.
• Forgetting the disableuhs patch and accumulating input/output errors on the SD card once the PCIe port is populated.
• Leaving an /etc/fstab with inconsistent UUIDs after reformatting: check blkid before rebooting.
• Insufficient power supply: the SSD peak current added to the A311D causes a 5 V / 2 A charger to drop out.