Docker "network not found" - Fix Missing Networks in CI

A container or compose service referenced a Docker network that does not exist on the runner. Either it was never created or it was pruned away.

What this error means

A docker run --network <name> or docker compose up fails with network <name> not found, or compose reports a network "declared as external" but missing.

docker output

Error response from daemon: network mynet not found
# compose:
network "shared" declared as external, but could not be found

Common causes

External network never created

A compose file marks a network external: true, expecting it to pre-exist, but no docker network create ran in the pipeline.

A prune removed the network

docker system prune or network prune between steps can delete an unused network that a later step expects.

Networks not shared across jobs

A network created in one job does not exist in another job on a different runner.

How to fix it

Create the external network before use

Provision the network as an explicit step, or let compose manage it (drop external).

Terminal

docker network create shared || true
docker compose up -d

Let compose own the network

Remove external: true so compose creates and tears down the network itself.

docker-compose.yml

networks:
  shared:
    # no 'external: true' - compose creates it

How to prevent it

Create external networks explicitly before steps that need them.
Avoid pruning networks mid-pipeline when later steps depend on them.
Prefer compose-managed networks for self-contained jobs.