Docker Compose "Bind for 0.0.0.0:5432 failed: port is already allocated"

If docker compose up fails to start a container because another project or container is already using the same host port, the container is created but never starts:

Error response from daemon: failed to set up container networking: driver failed programming external connectivity on endpoint <project>-db-1 (<endpoint-id>): Bind for 0.0.0.0:5432 failed: port is already allocated

This is common when running two projects side by side that both publish a database (5432), Redis (6379) or a web server (80/8000) on the host.

Cause

The service has a ports: entry such as "5432:5432", which binds the container port to the same port on the host. Only one process can hold a host port, so the second project’s container cannot start.

Often the published port is not needed at all: other services in the same Compose project reach the database over the internal network by service name (for example db:5432), not through the host.

Fix

Leave the original docker-compose.yml untouched and add an override file. This is useful when the Compose file belongs to someone else or is shared with a team.

Create an override file, for example compose.no-ports.yml:

services:
    db:
        ports: !reset []

Then start the project with both files:

docker compose -f docker-compose.yml -f compose.no-ports.yml up -d

The db service now publishes nothing on the host, and other containers in the project still reach it at db:5432.

If the port is still needed from the host

Publish it on a free host port instead, using !override to replace the list:

services:
    db:
        ports: !override
            - "5433:5432"

Then connect from the host on localhost:5433.

Verify

docker compose -f docker-compose.yml -f compose.no-ports.yml ps

Every service should show as running. To see what currently holds the conflicting host port:

docker ps --filter "publish=5432"
# or, for processes outside Docker
sudo lsof -iTCP:5432 -sTCP:LISTEN

Notes

• Plain overrides do not work for ports. Compose merges ports from multiple files by appending, so an override containing ports: ["5433:5432"] keeps the original 5432:5432 as well and still fails. !reset (clear the list) and !override (replace the list) are what make the override take effect.
• !reset and !override need Docker Compose v2.24.0 or later. Check with docker compose version.
• The same approach works for volumes, environment and other list or map fields that Compose merges rather than replaces.
• Alternatively, stop the other project with docker compose -p <other-project> down, but that is not an option if both need to run at once.