The image bundles bitcoin-core and starts up as unprivileged user 1000:1000. It expects one /data volume.

The volume must be writable by 1000:1000 or any corresponding uid:gid if userns-remap is enabled.

The default configuration file will be pre-created if volume does not contain the config already. You may also mount your desired config directly to /data/bitcoin.conf

# It's supposed you have pre-created the data volume with correct permissions

# Actually you can both path cli args directly to bitcoind and at the same time pass an existing config.
# Or pre-create a config in the data volume as you wish.
docker run -d -v /path/to/bitcoin.conf:/data/bitcoin.conf -v data:/data plasmops/bitcoind:0.17.0.1 -printtoconsole

We use the defaults of bitcoin-core, but set rpcuser=bitcoinrpc and rpcpassword=plasmops. Do not forget to override when in production!