unbd

unbd - micro implementation of a network block device in python.

What for?

Use this package for mounting folders on wifi-enabled micropython devices such as ESP8266 and ESP32.

Install

If you want to use unbd directly install it on your micropython device through mpremote

mpremote mip install github:pulkin/unbd

To use unbd with cpython and/or in command-line environment use pip

pip install git+https://github.com/pulkin/unbd

How to use

First, install nbd server on your host computer: it will serve file system images over your local network. Then, use the snapmount script on the host or the unbd module on the micropython device directly.

• using snapmount

  1. Install cpython package on your host computer

     pip install git+https://github.com/pulkin/unbd
     

  2. Connect your wifi-enabled micropython device to a serial port on your host computer
  3. Mount your source folder src with

     snapmount src
     

  Note that snapmount uses wifi to communicate host your micropython device in station mode with the host computer. It will attempt to deduce network credentials through Network Manager on Linux (nmcli). You may explicitly supply credentials through --ssid and --passphrase.

• manually

  1. Start NBD server on the host machine

     nbd-server 33567 /full/path/to/fs.img -d
     

  2. Connect and install unbd on your micropython device

     mpremote mip install github:pulkin/unbd
     

  3. Mount the remote device

     from unbd import connect
     import os
     os.mount(connect('host-ip-address', 33567, open=True), "/mount")
     

  Note that fs.img located on the host machine contains FAT image.

Key features

• fully virtual file system over wifi
• relatively high performance
• minimal setup needed
• tiny footprint
• no flash storage used (and no performance degradation for intensive IO)

Performance

The mounted filesystem speeds range from several Kbps up to 100 Kbps in read and write. The final throughput is roughly the ratio block_size / network_latency. Thus, to achieve maximal performance:

• increase block_size (4096 is about the saturated maximum)
• ensure the wireless connection is stable

FAT filesystem is, in general, twice as fast as littlefs for reading large files.

Real-world benchmarks

Case	LittleFS 512	FAT 512	FAT 4096
App: ~100Kb, tens of source files	33s	12s	9s

Examples

unbd

Simply mount the partition with default values (micropython)

from unbd import connect
os.mount(connect(host, port, open=True), "/mount")

Mount littlefs with a large block size

os.mount(os.VfsLfs2(connect(host, port, block_size=4096), readsize=4096), "/mount")

Mount FAT with a large block size

os.mount(os.VfsFat(connect(host, port, block_size=4096)), "/mount")

Develop and test with snapmount

See also bare-metal tests for this package.

Running a test script test.py from src

from snapmount import mounted

with mounted('src', endpoint="/", **kwargs) as board:
    out, err = board.exec_raw("import test")
    assert len(err) == 0

Same with snapmount in command line

snapmount src --ssid="ssid" --passphrase="secret" --endpoint=/ --payload="import test"

More options

snapmount src --verbose \
  --ssid="ssid" \
  --passphrase="secret" \
  --soft-reset \ 
  --endpoint=/ \
  --fs=fat \
  --block-size=4096 \
  --payload="import test"

License

LICENSE.md