Building Rootfs for Lichee Pi Nano

This article describes how to build a filesystem with Buildroot for Lichee Nano, including getting the source code from GitHub, configuring compilation options, compiling, and installing the rootfs onto the SD card’s second partition — the layout used by the linux-sunxi Bootable SD card convention

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1. Get the Buildroot Source Code

You can download Buildroot from the official site or GitHub:

Download from GitHub

git clone --branch 2023.02.11 --depth=1 https://github.com/buildroot/buildroot.git
cd buildroot/

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2. Pre-Compile Configuration

Navigate to the Buildroot directory and enter the configuration page:

make menuconfig

If a .config file exists, delete it first:

rm .config -fv

Modify the following configuration — these match the F1C100s core (ARM926EJ-S / ARMv5TE, no hardware FPU), the same constraint that governs the kernel toolchain choice:

• Target options
  • Target Architecture: ARM (little endian)
  • Target Binary Format: ELF
  • Target Architecture Variant: arm926t
  • Enable VFP extension support: unchecked — the Nano has no VFP unit; leaving this checked builds userspace that will crash/fail to run on this board
  • Target ABI: EABI
  • Floating point strategy: Soft float
  • ARM instruction set: ARM
• Toolchain
  • C library: musl or uClibc-ng (recommended — see size comparison below; avoid glibc on an 8MB-class flash target)
• System configuration
  • (Lichee Pi) System hostname
  • (licheepi) Root password
  • [*] Run a getty (login prompt) after boot → enable, port ttyS0, baud 115200 — this is what actually gives you a login prompt over serial; see the /etc/inittab note in step 5
  • [*] remount root filesystem read-write during boot

This mirrors the same soft-float requirement covered in the kernel build post — Buildroot’s own toolchain here is independent of the one used for the kernel, so it needs to be configured for soft-float ARMv5 separately; it does not inherit the choice made for CROSS_COMPILE when building zImage.

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3. Compile

Simply run:

make

Note: Multi-threaded compilation is not supported by top-level make. Depending on download speed, compilation may take from half an hour to half a day.

Once successful, you’ll get the filesystem tarball:
output/images/rootfs.tar

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4. Installing the Rootfs — SD card second partition (recommended path)

This is the path actually validated on real hardware for this board: a 2-partition SD card, FAT32 boot partition (zImage + .dtb + boot.scr) as partition 1, and the rootfs as partition 2, formatted ext4. This matches both the official Lichee-Pi rootfs.rst guide and the general linux-sunxi SD-card convention, and it’s the exact layout that got a full kernel boot log ending in “root filesystem mounted” earlier in this series — the only thing missing at that point was the rootfs content itself, which this step fills in.

# Format partition 2 as ext4 if you haven't already (adjust device node!)
sudo mkfs.ext4 /dev/sdX2

# Mount and extract
sudo umount /dev/sdX2 2>/dev/null
sudo mount /dev/sdX2 /mnt
sudo cp ./output/images/rootfs.tar /mnt/
sudo tar -xf /mnt/rootfs.tar -C /mnt/
sudo rm /mnt/rootfs.tar
sync
sudo umount /dev/sdX2

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5. Startup Log

With rootfs correctly placed on mmcblk0p2 and /etc/inittab configured for ttyS0, boot proceeds past the point where the previous post’s kernel-only test stopped (Kernel panic - not syncing: No working init found) straight through to a working login prompt:

    1.537024] Freeing unused kernel memory: 1024K
[    1.655580] EXT4-fs (mmcblk0p2): re-mounted. Opts: data=ordered
Seeding 2048 bit[    1.874288] random: crng init done
s and crediting
Saving 2048 bits of creditable seed for next boot
Starting syslogd: OK
Starting klogd: OK
Running sysctl: OK
Starting network: OK

Welcome to Buildroot
Lichee login: licheepi
Password: 

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References

• Buildroot Official Site
• Buildroot GitHub
• Lichee Nano rootfs guide (Lichee-Pi/Lichee-Nano-Doc-us-english)
• linux-sunxi: Bootable SD card