Ollama: listen tcp 127.0.0.1:11434 bind: address already in use

Environment: Ollama on Linux/macOS/Windows; especially common on Linux where the systemd unit and a manual ollama serve both try to bind.

Severity: low — only blocks startup; no data risk.

• The Linux installer registers a systemd unit that auto-starts; running ollama serve again fights it
• macOS LaunchAgent left over from a previous install
• A second Ollama instance (e.g. one inside Docker, one on host) competing for 11434
• Stale process from a crashed prior run that didn't release the port
• LM Studio's local server occasionally collides on the same port if reconfigured

1. Find what's holding the port:

# Linux / macOS
sudo lsof -i :11434
ss -tulpn | grep 11434
# Windows PowerShell
Get-NetTCPConnection -LocalPort 11434 | Select-Object OwningProcess

2. If it's the systemd unit, either let it serve and don't run ollama serve manually, or override the unit:

sudo systemctl status ollama
# Stop and disable if you prefer manual control
sudo systemctl stop ollama
sudo systemctl disable ollama
ollama serve

3. Override the listen host/port via env-file (production-grade):

sudo systemctl edit ollama
# In the editor:
[Service]
Environment="OLLAMA_HOST=0.0.0.0:11500"

sudo systemctl daemon-reload && sudo systemctl restart ollama

4. Kill stale processes:

pkill -f ollama && sleep 1 && ollama serve

5. Run on a different port if you legitimately need two:

OLLAMA_HOST=0.0.0.0:11500 ollama serve