Containers with Read-Only Root Filesystem

By default, CloudQuery requires a read-write file system to create a socket file used by the plugins to communicate with the CLI. It is however not possible to create a read-write socket on a read-only file system. For this to work, a plugin needs to be started as a gRPC server locally.

Creating a container that works with a read-only file system

To create a container that works with a read-only file system, you will need the following:

a CloudQuery config file that is used to install the required plugins
a CloudQuery config file that contains the specs needed for the sync
a start script used as an entry point for the container that will start the plugins and run the sync

In the example below, we will use the XKCD (opens in a new tab) source plugin and PostgreSQL (opens in a new tab) destination plugin.

Create a config file for the installation

This config file should reference the plugins that you want to install with the actual source where they should be downloaded from:

install.yaml

kind: source
spec:
  name: xkcd
  path: hermanschaaf/xkcd
  version: v2.0.0
  destinations: ["postgresql"]
  tables: ["*"]
---
kind: destination
spec:
  name: "postgresql"
  registry: "cloudquery"
  path: "cloudquery/postgresql"
  version: "v7.3.4"

Create a config file for the sync

This config file should reference the plugins running as gRPC servers (fill in the connection_string). We will run XKCD on port 7778 and PostgreSQL on port 7779:

sync.yaml

kind: source
spec:
  name: xkcd
  registry: grpc
  path: localhost:7778
  destinations: ["postgresql"]
  tables: ["*"]
---
kind: destination
spec:
  name: "postgresql"
  registry: grpc
  path: localhost:7779
  spec:
    connection_string: "[REDACTED]"

Create a start script to start the plugins

This shell script will start the plugins and the sync with the provided parameters when we run the container. To make it easier to maintain, we will use the find command to get the path to the actual plugin binary. This way, we don't have to worry about the version of the plugin.

#!/bin/sh
# get path to the xkcd plugin:
xkcd_plugin_path=$(find .cq -regex ".*/xkcd/.*/plugin")
# get path to the postgresql plugin:
postgresql_plugin_path=$(find .cq -regex ".*/postgresql/.*/plugin")

# start the plugins and run the sync with the provided parameters:
sh -c "${xkcd_plugin_path} serve --address localhost:7778" & \
sh -c "${postgresql_plugin_path} serve --address localhost:7779" & \
/app/cloudquery $@

Connecting it all together

We will use the ghcr.io/cloudquery/cloudquery:latest container as a base and add all the files in it. Then we will override the entry point with our start script:

FROM ghcr.io/cloudquery/cloudquery:latest
WORKDIR /app
# this is the install.yaml file we created above
COPY ./install.yaml /app/install.yaml
# install the plugins
RUN /app/cloudquery plugin install install.yaml
# add the sync config file
COPY ./sync.yaml /app/sync.yaml
# add the start script
COPY --chmod=0755 ./start.sh /app/start.sh
# override the start script
ENTRYPOINT [ "/app/start.sh"]

Run the Container

First, build the container as you would normally do:

docker build ./ -t my-cq-container:latest

Run the container with --read-only option and a command to pass to our start script. You will also need to add the --no-log-file option to skip logging to a file. Here is an example:

docker run --read-only --add-host=host.docker.internal:host-gateway my-cq-container:latest --no-log-file sync sync.yaml