6.7 KiB
eMMC Multi-Boot Setup — Orange Pi 3B
Status: Procedural reference. Last verified: 2026-06-02 (discussion with Jez).
Goal
Boot multiple ARM64 OSes from the OPi 3B's onboard 256GB eMMC, with a u-boot boot menu (extlinux.conf) appearing at power-on. No SD card needed after setup.
Planned OSes: Orange Pi OS (Arch), Armbian, NixOS
SPI NOR flash was erased via maskrom and is unused going forward.
Boot Chain (after SPI erase)
BootROM → SPI (empty, skip) → microSD (if inserted) → eMMC boot partition → extlinux.conf → menu → kernel
If microSD is inserted and has a valid bootloader, it takes priority over eMMC. Useful as a lifeboat/rescue path — if eMMC boot breaks, pop in the SD card and you're back.
Partition Layout
Proposed new partition schema:
mmcblk1 (256GB eMMC)
├── mmcblk1boot0 (hardware boot partition — u-boot SPL + proper)
├── mmcblk1boot1 (unused mirror)
└── mmcblk1
├── mmcblk1p1 FAT32 1GB /boot (extlinux.conf, kernels, DTBs — shared)
├── mmcblk1p2 ext4 85GB root_opios (Orange Pi OS Arch)
├── mmcblk1p3 ext4 85GB root_armbian (Armbian)
└── mmcblk1p4 ext4 ~84GB root_nixos (NixOS)
Why a dedicated FAT32 boot partition?
u-boot reads extlinux.conf from a FAT, ext4, or btrfs partition. FAT32 is the most universally supported across distro kernel packages. A shared /boot means all three OSes drop their kernels and DTBs into one place, and a single extlinux.conf controls the menu. 1GB gives headroom for multiple kernel versions across all three OSes.
Step 1: Clone SD → eMMC
Move Orange Pi OS from the microSD card to eMMC and leave two more root paritions ready for other operating systems later.
1.1 — Identify devices
Run on the running Orange Pi OS (booted from SD):
lsblk
mount | grep mmcblk
Expected:
mmcblk0= SD card (current boot device)mmcblk1= eMMC (target boot device) Actual:mmcblk0= eMMC (target boot device)mmcblk1= SD card (current boot device)
Ground truth state with only OPi OS on SD card:
[jez@Rocky ~]$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
mtdblock0 31:0 0 16M 0 disk
mmcblk0 179:0 0 233G 0 disk
mmcblk0boot0 179:32 0 4M 1 disk
mmcblk0boot1 179:64 0 4M 1 disk
mmcblk1 179:96 0 238.4G 0 disk
├─mmcblk1p1 179:97 0 213.6M 0 part /boot
└─mmcblk1p2 179:98 0 238.2G 0 part /
zram0 254:0 0 0B 0 disk
1.2 — Wipe eMMC partition table
Destroys everything on eMMC. Skip if eMMC is already empty.
sudo sgdisk --zap-all /dev/mmcblk0
sudo blkdiscard /dev/mmcblk0 # optional
1.3 — Partition eMMC
sudo gdisk /dev/mmcblk0
In gdisk interactive mode:
o (new GPT)
n 1 default +1G ef00 name=boot
n 2 default +85G 8300 name=root_opios
n 3 default +85G 8300 name=root_armbian
n 4 default default 8300 name=root_nixos
w (write, confirm 'y')
1.4 — Create filesystems
sudo mkfs.vfat -F 32 -n BOOT /dev/mmcblk0p1
sudo mkfs.ext4 -L root_opios /dev/mmcblk0p2
sudo mkfs.ext4 -L root_armbian /dev/mmcblk0p3
sudo mkfs.ext4 -L root_nixos /dev/mmcblk0p4
1.5 — Mount and rsync the live rootfs
sudo mkdir -p /mnt/root_opios
sudo mount /dev/mmcblk0p2 /mnt/root_opios
sudo mkdir -p /mnt/root_opios/boot
sudo mount /dev/mmcblk0p1 /mnt/root_opios/boot
sudo rsync -axHAWX --info=progress2 / /mnt/root_opios/
Flags: archive, stay-on-filesystem (critical — skips /proc, /sys, /dev), preserve hardlinks/ACLs/xattrs, copy whole files (faster locally).
1.6 — Bind mount virtual filesystems
sudo mkdir -p /mnt/root_opios/{proc,sys,dev,run,tmp}
sudo mount --bind /proc /mnt/root_opios/proc
sudo mount --bind /sys /mnt/root_opios/sys
sudo mount --bind /dev /mnt/root_opios/dev
sudo mount --bind /run /mnt/root_opios/run
1.7 — Update fstab
sudo blkid /dev/mmcblk0p1 /dev/mmcblk0p2
Edit /mnt/root_opios/etc/fstab. Replace old SD card references with:
UUID=<boot-UUID> /boot vfat defaults,noatime 0 2
UUID=<root_opios-UUID> / ext4 defaults,noatime 0 1
1.8 — Write extlinux.conf
uname -r
find /mnt/root_opios/boot -name "*.dtb" | grep orangepi-3b
Create /mnt/root_opios/boot/extlinux/extlinux.conf:
TIMEOUT 10
DEFAULT orangepi-os
LABEL orangepi-os
MENU LABEL Orange Pi OS
LINUX /vmlinuz-<kernel-version>
INITRD /initrd.img-<kernel-version>
FDT /dtbs/rockchip/rk3566-orangepi-3b.dtb
APPEND root=UUID=<root_opios-UUID> rootwait console=ttyS2,115200 console=tty1
1.9 — Install u-boot to eMMC hardware boot partition
First check if Orange Pi OS ships u-boot binaries:
find / -name "idbloader.img" -o -name "u-boot.itb" -o -name "*loader*" 2>/dev/null
If files exist at known paths, use them. If not, extract from SD card:
sudo dd if=/dev/mmcblk1 of=idbloader.img bs=512 count=16384
sudo dd if=/dev/mmcblk1 of=u-boot.itb bs=512 skip=16384 count=8192
Write to eMMC hardware boot partition:
echo 0 | sudo tee /sys/block/mmcblk0/force_ro
sudo mmc bootpart enable 1 1 /dev/mmcblk0
sudo dd if=idbloader.img of=/dev/mmcblk0boot0 bs=512 seek=64
sudo dd if=u-boot.itb of=/dev/mmcblk0boot0 bs=512 seek=16384
sudo sync
1.10 — Clean up and test
sudo umount /mnt/root_opios/boot
sudo umount /mnt/root_opios/proc /mnt/root_opios/sys /mnt/root_opios/dev /mnt/root_opios/run
sudo umount /mnt/root_opios
sudo sync
sudo poweroff
Remove SD card. Power on. u-boot logo → boot menu → Orange Pi OS from eMMC.
Troubleshooting
| Symptom | Likely cause | Fix |
|---|---|---|
| u-boot logo, then blank screen | EDID/HDMI handshake | Add video=HDMI-A-1:1920x1080@60e to APPEND line |
| "No bootable device" | u-boot not written to eMMC boot part | Re-do step 1.9 |
| Kernel panic: can't find root | Wrong UUID in extlinux.conf | Boot from SD, mount eMMC, fix UUID |
| Nothing on screen at all | SPI flash interference? HDMI? | Re-check SPI erase, try different monitor |
Step 2: Install Armbian
(To be documented — Armbian rootfs goes into root_armbian, kernel+DTB added to shared /boot, next LABEL added to extlinux.conf.)
Step 3: Install NixOS
(To be documented — NixOS rootfs goes into root_nixos. Likely the trickiest since NixOS generates its own /boot structure.)
Reference
- Rockchip boot flow: https://opensource.rock-chips.com/wiki_Boot_option
- U-boot extlinux format: https://docs.u-boot.org/en/stable/develop/distro.html
- OPi 3B bring-up:
docs/initial-bringup.md - Storage architecture:
docs/storage-architecture.md