Update setting-up-a-shared-folder.md

[amigthea]

added bindfs mount option

[BrownNPC]

Please merge this! it could have saved me hours of research

[BrownNPC]

Here's how you do a bi-directional mount using bindfs. I would appreciate if this guide could be added too.

This is useful for allowing waydroid to write files into your linux host.

For example, if we want to link our host ~/Downloads folder from within waydroid's filesystem as Download so that when you download a file in waydroid, it goes to your linux ~/Downloads folder.

First get the UID waydroid uses for folders.

export WAYDROID_ID=$(sudo stat -c '%u' ~/.local/share/waydroid/data/media)

next, we can use a command like this to mount a linux folder into waydroid.

sudo bindfs \
  --perms=u=rwx,g=rwx,o=rx \
  --force-group=$WAYDROID_ID \
  ~/LINUX_HOST_FOLDER \
  ~/.local/share/waydroid/data/media/0/WAYDROID_FOLDER

Bash script version (Click to reveal)

#!/usr/bin/env bash

# Exit on errors
set -e

# Usage check
if [ $# -ne 2 ]; then
    echo "Usage: $0 <host_folder> <waydroid_subfolder>"
    exit 1
fi

HOST_FOLDER="$1"
WAYDROID_SUB="$2"
WAYDROID_BASE="$HOME/.local/share/waydroid/data/media/0"
TARGET_FOLDER="$WAYDROID_BASE/$WAYDROID_SUB"

# Check host folder exists
if [ ! -d "$HOST_FOLDER" ]; then
    echo "Error: Host folder '$HOST_FOLDER' does not exist"
    exit 1
fi

# Detect Waydroid UID dynamically
if ! WAYDROID_UID=$(sudo stat -c '%u' "$WAYDROID_BASE" 2>/dev/null); then
    echo "Error: Could not determine Waydroid UID from '$WAYDROID_BASE'"
    exit 1
fi

# Create target folder if it doesn't exist
sudo mkdir -p "$TARGET_FOLDER"

# Perform the bindfs mount
sudo bindfs \
    --perms=u=rwx,g=rwx,o=rx \
    --force-group="$WAYDROID_UID" \
    "$HOST_FOLDER" \
    "$TARGET_FOLDER"

echo "Mounted '$HOST_FOLDER' → '$TARGET_FOLDER' with Waydroid UID $WAYDROID_UID"

Usage

# Allows waydroid to access host ~/Downloads folder. it will be available as Download inside of waydroid's filesystem
./bind-to-waydroid.sh ~/Downloads Download