Port already in use during deployment

April 30, 2026 · View on GitHub

Playbook ID: port-conflict Category: deploy Severity: medium Tags: port, conflict, binding, deploy, network

What this failure means

A container or service failed to start because the port it needs to bind to is already occupied by another process or a previous deployment that has not been fully removed.

Common log signals

port is already allocated
failed to bind to port
port conflict
cannot start service

Diagnosis

A container or service failed to start because the port it needs to bind to is already occupied by another process or a previous deployment that has not been fully removed.

In deploy contexts this usually means a host-port mapping is colliding during rollout, or a prior container still owns the port on the target node.

Fix steps

  1. Find the process occupying the port: lsof -i :<port> or ss -tlnp | grep <port>.
  2. In Kubernetes with host ports: ensure the old pod is fully terminated before the new one starts, or adjust the rollout strategy so the hand-off is serial.
  3. Check for stopped containers: docker ps -a | grep <image> and remove obsolete containers with docker rm.
  4. If using NodePort or HostPort in Kubernetes, verify no two pods on the same node request the same port.

Validation

  • Re-run the failing workflow step.
  • Confirm the original failure signature for Port already in use during deployment is gone.

Likely files to inspect

  • docker-compose.yml
  • docker-compose*.yml
  • k8s/**/*.yaml
  • deploy/**/*.yaml

Run Faultline

faultline analyze build.log
faultline explain port-conflict
faultline workflow build.log --json --mode agent

Search phrases this page answers

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  • Deploy: port already in use during deployment
  • port is already allocated
  • faultline explain port-conflict

Generated from playbooks/bundled/log/deploy/port-conflict.yaml. Do not edit directly — run make docs-generate.