How to Self-Host Semaphore: Web UI for Ansible 2026

TL;DR

Semaphore (MIT, ~10K GitHub stars, Go) is a web UI for running Ansible playbooks. Instead of SSH-ing into a server and running ansible-playbook commands, click a button in a clean web interface. Schedule playbooks, manage inventories, store credentials securely, and give team members access without sharing SSH keys. AWX (the open source Ansible Tower) requires 8GB+ RAM and complex setup. Semaphore runs in ~50MB RAM.

Key Takeaways

Semaphore: MIT, ~10K stars, Go — lightweight web UI for Ansible
Task scheduling: Run playbooks on a cron schedule — automated server maintenance
Inventory management: Store and manage Ansible inventories in the UI
Key/credential store: Securely store SSH keys, passwords, and vault passwords
Team access: Role-based access — give teammates specific project access
Lightweight: ~50MB RAM vs AWX's 8GB+ — runs on any small server

Semaphore vs AWX vs Ansible CLI

Feature	Semaphore	AWX	Ansible CLI
RAM usage	~50MB	~8GB+	N/A
Setup time	5 min	30+ min	N/A
Web UI	Yes (clean)	Yes (complex)	No
Scheduling	Yes	Yes	External (cron)
RBAC	Basic	Advanced	N/A
API	REST	REST	N/A
Workflow engine	No	Yes	No
Notifications	Email, Telegram, Slack	Email, Slack, webhook	N/A
Best for	Small-medium teams	Enterprise	Individual

Part 1: Docker Setup

# docker-compose.yml
services:
  semaphore:
    image: semaphoreui/semaphore:latest
    container_name: semaphore
    restart: unless-stopped
    ports:
      - "3000:3000"
    volumes:
      - semaphore_data:/var/lib/semaphore
    environment:
      SEMAPHORE_DB_DIALECT: bolt   # Or: postgres, mysql
      # For PostgreSQL:
      # SEMAPHORE_DB_DIALECT: postgres
      # SEMAPHORE_DB_HOST: db
      # SEMAPHORE_DB_PORT: 5432
      # SEMAPHORE_DB_NAME: semaphore
      # SEMAPHORE_DB_USER: semaphore
      # SEMAPHORE_DB_PASS: ${DB_PASSWORD}

      SEMAPHORE_ADMIN_PASSWORD: "${ADMIN_PASSWORD}"
      SEMAPHORE_ADMIN_NAME: admin
      SEMAPHORE_ADMIN_EMAIL: admin@yourdomain.com
      SEMAPHORE_ADMIN: admin

      SEMAPHORE_ACCESS_KEY_ENCRYPTION: "${ENCRYPTION_KEY}"  # openssl rand -base64 32

volumes:
  semaphore_data:

echo "ADMIN_PASSWORD=$(openssl rand -base64 16)" >> .env
echo "ENCRYPTION_KEY=$(openssl rand -base64 32)" >> .env

docker compose up -d

Part 2: HTTPS with Caddy

ansible.yourdomain.com {
    reverse_proxy localhost:3000
}

Part 3: Project Setup

Create a project

+ New Project
Name: Server Management

Add key store entries

Store credentials securely:

Key Store → + Add Key:
  
  # SSH key for server access:
  Name: Server SSH Key
  Type: SSH Key
  Private Key: (paste your private key)
  
  # Ansible Vault password:
  Name: Vault Password
  Type: Login with Password
  Password: your-vault-password
  
  # Git credentials:
  Name: Git Credentials
  Type: Login with Password
  Username: git-user
  Password: git-token

Add inventory

Inventory → + Add:

  # Static inventory:
  Name: Production Servers
  Type: Static
  Content:
    [webservers]
    web1.yourdomain.com
    web2.yourdomain.com
    
    [databases]
    db1.yourdomain.com
    
    [all:vars]
    ansible_user=deploy
    ansible_python_interpreter=/usr/bin/python3

Add repository

Repositories → + Add:
  Name: Playbooks
  URL: https://git.yourdomain.com/infra/ansible-playbooks.git
  Branch: main
  Access Key: Git Credentials (from key store)

Part 4: Running Playbooks

Create a task template

Task Templates → + Add:
  Name: Update All Servers
  Playbook: playbooks/update-servers.yml
  Inventory: Production Servers
  Repository: Playbooks
  Environment: (optional extra variables)
  Vault Password: Vault Password (from key store)

Run a task

Task Templates → Update All Servers → Run
Watch real-time output in the browser
See success/failure for each host
View full logs after completion

Extra variables

Pass variables at runtime:

{
  "target_version": "2.3.1",
  "restart_services": true,
  "dry_run": false
}

Part 5: Scheduling

Cron schedules

Task Templates → [template] → Schedules → + Add:
  Cron Expression: 0 3 * * *     # Daily at 3 AM
  # Or: 0 */6 * * *              # Every 6 hours
  # Or: 0 3 * * 0                # Weekly on Sunday

Common automation schedules

Task	Schedule	Cron
OS updates	Weekly Sunday 3 AM	`0 3 * * 0`
Certificate renewal	Daily 2 AM	`0 2 * * *`
Log rotation	Daily midnight	`0 0 * * *`
Backup verification	Weekly	`0 4 * * 1`
Security scan	Daily 5 AM	`0 5 * * *`
Docker prune	Weekly	`0 3 * * 6`

Part 6: Notifications

Email

Settings → Notifications → Email:
  SMTP Host: mail.yourdomain.com
  SMTP Port: 587
  From: semaphore@yourdomain.com

Settings → Notifications → Telegram:
  Bot Token: your-telegram-bot-token
  Chat ID: your-chat-id

Slack / Microsoft Teams

Settings → Notifications → Slack:
  Webhook URL: https://hooks.slack.com/services/...

Notifications trigger on:

Task success
Task failure
Schedule start

Part 7: Team Access

Add users

Settings → Users → + Add:
  Username: alice
  Email: alice@yourdomain.com
  Role: Manager / Task Runner / Guest

Roles

Role	Capabilities
Admin	Full access, manage users and projects
Manager	Create/edit templates, run tasks, manage inventories
Task Runner	Run existing templates only
Guest	View task history only

Project-level access

Each project can have different team members with different roles — a developer might have Task Runner access to staging but Guest access to production.

Part 8: REST API

BASE="https://ansible.yourdomain.com/api"

# Login and get token:
TOKEN=$(curl -s -X POST "$BASE/auth/login" \
  -H "Content-Type: application/json" \
  -d '{"auth": "admin", "password": "your-password"}' \
  | jq -r '.token')

# List projects:
curl "$BASE/projects" \
  -H "Authorization: Bearer $TOKEN" | jq '.[].name'

# Run a task:
curl -X POST "$BASE/project/1/tasks" \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "template_id": 1,
    "environment": "{\"target_version\": \"2.3.1\"}"
  }'

# Get task output:
curl "$BASE/project/1/tasks/42/output" \
  -H "Authorization: Bearer $TOKEN"

Maintenance

# Update:
docker compose pull
docker compose up -d

# Backup:
tar -czf semaphore-backup-$(date +%Y%m%d).tar.gz \
  $(docker volume inspect semaphore_semaphore_data --format '{{.Mountpoint}}')

# Logs:
docker compose logs -f semaphore

Why Self-Host Semaphore?

The case for self-hosting Semaphore comes down to three practical factors: data ownership, cost at scale, and operational control.

Data ownership is the fundamental argument. When you use a SaaS version of any tool, your data lives on someone else's infrastructure subject to their terms of service, their security practices, and their business continuity. If the vendor raises prices, gets acquired, changes API limits, or shuts down, you're left scrambling. Self-hosting Semaphore means your data and configuration stay on infrastructure you control — whether that's a VPS, a bare metal server, or a home lab.

Cost at scale matters once you move beyond individual use. Most SaaS equivalents charge per user or per data volume. A self-hosted instance on a $10-20/month VPS typically costs less than per-user SaaS pricing for teams of five or more — and the cost doesn't scale linearly with usage. One well-configured server handles dozens of users for a flat monthly fee.

Operational control is the third factor. The Docker Compose configuration above exposes every setting that commercial equivalents often hide behind enterprise plans: custom networking, environment variables, storage backends, and authentication integrations. You decide when to update, how to configure backups, and what access controls to apply.

The honest tradeoff: you're responsible for updates, backups, and availability. For teams running any production workloads, this is familiar territory. For individuals, the learning curve is real but the tooling (Docker, Caddy, automated backups) is well-documented and widely supported.

Server Requirements and Sizing

Before deploying Semaphore, assess your server capacity against expected workload.

Minimum viable setup: A 1 vCPU, 1GB RAM VPS with 20GB SSD is sufficient for personal use or small teams. Most consumer VPS providers — Hetzner, DigitalOcean, Linode, Vultr — offer machines in this range for $5-10/month. Hetzner offers excellent price-to-performance for European and US regions.

Recommended production setup: 2 vCPUs with 4GB RAM and 40GB SSD handles most medium deployments without resource contention. This gives Semaphore headroom for background tasks, caching, and concurrent users while leaving capacity for other services on the same host.

Storage planning: The Docker volumes in this docker-compose.yml store all persistent Semaphore data. Estimate your storage growth rate early — for data-intensive tools, budget for 3-5x your initial estimate. Hetzner Cloud and Vultr both support online volume resizing without stopping your instance.

Operating system: Any modern 64-bit Linux distribution works. Ubuntu 22.04 LTS and Debian 12 are the most commonly tested configurations. Ensure Docker Engine 24.0+ and Docker Compose v2 are installed — verify with docker --version and docker compose version. Avoid Docker Desktop on production Linux servers; it adds virtualization overhead and behaves differently from Docker Engine in ways that cause subtle networking issues.

Network: Only ports 80 and 443 need to be publicly accessible when running behind a reverse proxy. Internal service ports should be bound to localhost only. A minimal UFW firewall that blocks all inbound traffic except SSH, HTTP, and HTTPS is the single most effective security measure for a self-hosted server.

Backup and Disaster Recovery

Running Semaphore without a tested backup strategy is an unacceptable availability risk. Docker volumes are not automatically backed up — if you delete a volume or the host fails, data is gone with no recovery path.

What to back up: The named Docker volumes containing Semaphore's data (database files, user uploads, application state), your docker-compose.yml and any customized configuration files, and .env files containing secrets.

Backup approach: For simple setups, stop the container, archive the volume contents, then restart. For production environments where stopping causes disruption, use filesystem snapshots or database dump commands (PostgreSQL pg_dump, SQLite .backup, MySQL mysqldump) that produce consistent backups without downtime.

For a complete automated backup workflow that ships snapshots to S3-compatible object storage, see the Restic + Rclone backup guide. Restic handles deduplication and encryption; Rclone handles multi-destination uploads. The same setup works for any Docker volume.

Backup cadence: Daily backups to remote storage are a reasonable baseline for actively used tools. Use a 30-day retention window minimum — long enough to recover from mistakes discovered weeks later. For critical data, extend to 90 days and use a secondary destination.

Restore testing: A backup that has never been restored is a backup you cannot trust. Once a month, restore your Semaphore backup to a separate Docker Compose stack on different ports and verify the data is intact. This catches silent backup failures, script errors, and volume permission issues before they matter in a real recovery.

Security Hardening

Self-hosting means you are responsible for Semaphore's security posture. The Docker Compose setup provides a functional base; production deployments need additional hardening.

Always use a reverse proxy: Never expose Semaphore's internal port directly to the internet. The docker-compose.yml binds to localhost; Caddy or Nginx provides HTTPS termination. Direct HTTP access transmits credentials in plaintext. A reverse proxy also centralizes TLS management, rate limiting, and access logging.

Strong credentials: Change default passwords immediately after first login. For secrets in docker-compose environment variables, generate random values with openssl rand -base64 32 rather than reusing existing passwords.

Firewall configuration:

ufw default deny incoming
ufw allow 22/tcp
ufw allow 80/tcp
ufw allow 443/tcp
ufw enable

Internal service ports (databases, admin panels, internal APIs) should only be reachable from localhost or the Docker network, never directly from the internet.

Network isolation: Docker Compose named networks keep Semaphore's services isolated from other containers on the same host. Database containers should not share networks with containers that don't need direct database access.

VPN access for sensitive services: For internal-only tools, restricting access to a VPN adds a strong second layer. Headscale is an open source Tailscale control server that puts your self-hosted stack behind a WireGuard mesh, eliminating public internet exposure for internal tools.

Update discipline: Subscribe to Semaphore's GitHub releases page to receive security advisory notifications. Schedule a monthly maintenance window to pull updated images. Running outdated container images is the most common cause of self-hosted service compromises.

Troubleshooting Common Issues

Container exits immediately or won't start

Check logs first — they almost always explain the failure:

docker compose logs -f semaphore

Common causes: a missing required environment variable, a port already in use, or a volume permission error. Port conflicts appear as bind: address already in use. Find the conflicting process with ss -tlpn | grep PORT and either stop it or change Semaphore's port mapping in docker-compose.yml.

Cannot reach the web interface

Work through this checklist:

Confirm the container is running: docker compose ps
Test locally on the server: curl -I http://localhost:PORT
If local access works but external doesn't, check your firewall: ufw status
If using a reverse proxy, verify it's running and the config is valid: caddy validate --config /etc/caddy/Caddyfile

Permission errors on volume mounts

Some containers run as a non-root user. If the Docker volume is owned by root, the container process cannot write to it. Find the volume's host path with docker volume inspect VOLUME_NAME, check the tool's documentation for its expected UID, and apply correct ownership:

chown -R 1000:1000 /var/lib/docker/volumes/your_volume/_data

High resource usage over time

Memory or CPU growing continuously usually indicates unconfigured log rotation, an unbound cache, or accumulated data needing pruning. Check current usage with docker stats semaphore. Add resource limits in docker-compose.yml to prevent one container from starving others. For ongoing visibility into resource trends, deploy Prometheus + Grafana or Netdata.

Data disappears after container restart

Data stored in the container's writable layer — rather than a named volume — is lost when the container is removed or recreated. This happens when the volume mount path in docker-compose.yml doesn't match where the application writes data. Verify mount paths against the tool's documentation and correct the mapping. Named volumes persist across container removal; only docker compose down -v deletes them.

Keeping Semaphore Updated

Semaphore follows a regular release cadence. Staying current matters for security patches and compatibility. The update process with Docker Compose is straightforward:

docker compose pull          # Download updated images
docker compose up -d         # Restart with new images
docker image prune -f        # Remove old image layers (optional)

Read the changelog before major version updates. Some releases include database migrations or breaking configuration changes. For major version bumps, test in a staging environment first — run a copy of the service on different ports with the same volume data to validate the migration before touching production.

Version pinning: For stability, pin to a specific image tag in docker-compose.yml instead of latest. Update deliberately after reviewing the changelog. This trades automatic patch delivery for predictable behavior — the right call for business-critical services.

Post-update verification: After updating, confirm Semaphore is functioning correctly. Most services expose a /health endpoint that returns HTTP 200 — curl it from the server or monitor it with your uptime tool.

See all open source DevOps tools at OSSAlt.com/categories/devops.

The SaaS-to-Self-Hosted Migration Guide (Free PDF)