paularlott/knot-postgres repository overview

⁠knot-postgres

A PostgreSQL⁠ image for knot⁠ spaces. It wraps the official postgres image with the knot entrypoint, so a PostgreSQL instance running inside a space gets the same agent integration, rsyslog logging and startup hooks as every other knot base image. It is otherwise a standard PostgreSQL container and accepts the usual PostgreSQL environment variables.

⁠Tags

All tags are multi-arch (linux/amd64, linux/arm64); see Docker Hub⁠ for the current list.

Each release is also tagged <version>-<BUILD_DATE>.

⁠Usage

docker run -d \
  -p 5432:5432 \
  -e POSTGRES_PASSWORD=changeme \
  -e KNOT_SERVER=https://knot.example.com \
  -v pg_data:/var/lib/postgresql/data \
  paularlott/knot-postgres:18

In a knot space, the password is typically set from the user's Service Password:

environment:
  - KNOT_SERVER=${{.server.url}}
  - KNOT_USER=postgres
  - POSTGRES_PASSWORD=${{.user.service_password}}

Connect to the running server (from the host or another space) via knot port forwarding:

knot forward port 127.0.0.1:5432 <space> 5432

⁠How it works

The image layers the knot entrypoint on top of the official PostgreSQL image. On startup the entrypoint:

1. Forwards KNOT_USER to postgres.
2. If KNOT_SERVER is set, downloads and starts the knot agent (as postgres).
3. Starts rsyslog and forwards logs to the agent's syslog port.
4. Runs scripts in /etc/knot-startup.d/ and ~/.knot-startup.d/.
5. execs PostgreSQL's original docker-entrypoint.sh⁠ with postgres.

⁠PostgreSQL customizations

• Home directory — the postgres user's home is relocated from /var/lib/postgresql (the data directory) to /home/postgres, so the knot agent's state and user startup hooks live under /home/postgres/.knot and ~/.knot-startup.d/ instead of colliding with database files.
• Logging — PostgreSQL's error log is captured by piping the server's stderr to rsyslog (tag postgres).

⁠Environment variables

Plus all standard PostgreSQL variables (POSTGRES_PASSWORD, POSTGRES_USER, POSTGRES_DB, POSTGRES_INITDB_ARGS, …) and config mounted under $PGDATA (default /var/lib/postgresql/data).

⁠Exposed ports

⁠Volumes

• /var/lib/postgresql/data — the PostgreSQL data directory (PGDATA); persist this across restarts.

⁠License

PostgreSQL is PostgreSQL License⁠ (similar to BSD/MIT). This image's packaging — the Dockerfile, knot-entrypoint and supporting scripts/configs — is Apache License 2.0⁠.

Source: paularlott/knot-base-images⁠.