Blog/content/post/17-semaphore-ui-interface-ansible-terraform.md

---
slug: semaphore-ui-interface-ansible-terraform
title: Semaphore UI, a Great Interface for Ansible & Terraform
description: Demonstration of Semaphore UI, a web interface to run Ansible playbooks, Terraform code and even more. Installation with Docker and quick examples.
date: 2026-02-09
draft: true
tags:
  - semaphore-ui
  - ansible
  - terraform
  - proxmox
  - docker
categories:
  - homelab
---
## Intro

In my homelab, I like to play with tools like Ansible and Terraform. The primary interface is the CLI, which I love, but sometimes a fancy web UI is just nice.

After setting up my OPNsense cluster, I wanted a way to keep it up to date on a schedule. Automation means Ansible to me, but how do you automate and schedule playbooks?

At work I use Red Hat Ansible Automation Platform, which is great, but overkill for my lab. That’s how I found Semaphore UI. Let’s see what it can do.

---
## What is Semaphore UI

[Semaphore UI](https://semaphoreui.com/docs/) is a sleek web interface designed to run automation with tools like Ansible and Terraform, and even Bash, Powershell or Python scripts.

Initially began as Ansible Semaphore, a web interface created to provide a simple front-end for running solely Ansible playbooks. Over time the community evolved the project into a multi-tool automation control plane.

It is a self-contained Go application with minimal dependencies capable of using different database backend, such as PostgreSQL, MySQL, or BoltDB.

---
## Installation

Semaphore UI supports several [installation](https://semaphoreui.com/docs/category/installation) methods: Docker, Kubernetes, package manager or simple binary file.

I used Docker for my setup, you can see how I currently deploy application in this [post]({{< ref "post/16-how-I-deploy-application" >}})

Here my `docker-compose.yml` file I've configured using PostgreSQL:
```yaml
services:
  semaphore:
    image: semaphoreui/semaphore:v2.16.45
    container_name: semaphore_ui
    environment:
      - TZ=Europe/Paris
      - SEMAPHORE_DB_USER=${POSTGRES_USER}
      - SEMAPHORE_DB_PASS=${POSTGRES_PASSWORD}
      - SEMAPHORE_DB_HOST=postgres
      - SEMAPHORE_DB_PORT=5432
      - SEMAPHORE_DB_DIALECT=postgres
      - SEMAPHORE_DB=${POSTGRES_DB}
      - SEMAPHORE_PLAYBOOK_PATH=/tmp/semaphore/
      - SEMAPHORE_ADMIN_PASSWORD=${SEMAPHORE_ADMIN_PASSWORD}
      - SEMAPHORE_ADMIN_NAME=${SEMAPHORE_ADMIN_NAME}
      - SEMAPHORE_ADMIN_EMAIL=${SEMAPHORE_ADMIN_EMAIL}
      - SEMAPHORE_ADMIN=${SEMAPHORE_ADMIN}
      - SEMAPHORE_ACCESS_KEY_ENCRYPTION=${SEMAPHORE_ACCESS_KEY_ENCRYPTION}
      - SEMAPHORE_LDAP_ACTIVATED='no'
      # - SEMAPHORE_LDAP_HOST=dc01.local.example.com
      # - SEMAPHORE_LDAP_PORT='636'
      # - SEMAPHORE_LDAP_NEEDTLS='yes'
      # - SEMAPHORE_LDAP_DN_BIND='uid=bind_user,cn=users,cn=accounts,dc=local,dc=shiftsystems,dc=net'
      # - SEMAPHORE_LDAP_PASSWORD='ldap_bind_account_password'
      # - SEMAPHORE_LDAP_DN_SEARCH='dc=local,dc=example,dc=com'
      # - SEMAPHORE_LDAP_SEARCH_FILTER="(\u0026(uid=%s)(memberOf=cn=ipausers,cn=groups,cn=accounts,dc=local,dc=example,dc=com))"
    depends_on:
      - postgres
    networks:
      - backend
      - web
    labels:
      - traefik.enable=true
      - traefik.http.routers.semaphore.rule=Host(`semaphore.vezpi.com`)
      - traefik.http.routers.semaphore.entrypoints=https
      - traefik.http.routers.semaphore.tls.certresolver=letsencrypt
      - traefik.http.services.semaphore.loadbalancer.server.port=3000
    restart: unless-stopped

  postgres:
    image: postgres:14
    hostname: postgres
    container_name: semaphore_postgres
    volumes:
     - /appli/data/semaphore/db:/var/lib/postgresql/data
    environment:
      - POSTGRES_USER=${POSTGRES_USER}
      - POSTGRES_PASSWORD=${POSTGRES_PASSWORD}
      - POSTGRES_DB=${POSTGRES_DB}
    networks:
      - backend
    restart: unless-stopped

networks:
  backend:
  web:
    external: true
```

To generate the encrypting access keys, I use this command:
```bash
head -c32 /dev/urandom | base64
```

With Semaphore running, let’s take a quick tour of the UI and wire it up to a repo.

---
## Discovery

After starting the stack, I can reach the login page at the URL:
![Page de connexion de Semaphore UI](img/semaphore-login-page.png)

To log in, I use the credentials defined by `SEMAPHORE_ADMIN_NAME`/`SEMAPHORE_ADMIN_PASSWORD`.

On first login, Semaphore prompt me to create a project. I created the Homelab project:
![Page de création de projet de Semaphore UI](img/semaphore-create-project.png)

The first thing I want to do is to add my *homelab* repository (you can find its mirror on Github [here](https://github.com/Vezpi/homelab)). In `Repository`, I click the `New Repository` button, and add the repo URL. I don't specify credentials because the repo is public:
![Page d'ajout de dépôt de Semaphore UI](img/semaphore-add-repository.png)

ℹ️ Before continue, I deploy 3 VMs for testing purpose: `sem01`, `sem02` and `sem03`. I created them using Terraform with [this project](https://github.com/Vezpi/Homelab/tree/main/terraform/projects/semaphore-vms).

To interact with these VMs I need to configure credentials. In the the `Key Store`, I add the first credential, a SSH key for my user:
![Page d'ajout d'une nouvelle clé de Semaphore UI](img/semaphore-create-new-ssh-key.png)

Then I create a new `Inventory`. I'm using the Ansible inventory format (the only one available). I select the SSH key previously created and select the type as `Static`. In the fields I enter the 3 hosts created with their FQDN:
![Page de création d'un inventaire statique de Semaphore UI](img/semaphore-create-new-static-inventory.png)

✅ With a project, repo, credentials, and inventory in place, I can move forward and test to run an Ansible playbook.

---
## Launching an Ansible playbook

I want to test something simple, install a web server with a custom page on these 3 VMs, I create the playbook `install_nginx.yml`:
```yaml
---
- name: Demo Playbook - Install Nginx and Serve Hostname Page
  hosts: all
  become: true

  tasks:
    - name: Ensure apt cache is updated
      ansible.builtin.apt:
        update_cache: true
        cache_valid_time: 3600

    - name: Install nginx
      ansible.builtin.apt:
        name: nginx
        state: present

    - name: Create index.html with hostname
      ansible.builtin.copy:
        dest: /var/www/html/index.html
        content: |
          <html>
          <head><title>Demo</title></head>
          <body>
              <h1>Hostname: {{ inventory_hostname }}</h1>
          </body>
          </html>
        owner: www-data
        group: www-data
        mode: "0644"

    - name: Ensure nginx is running
      ansible.builtin.service:
        name: nginx
        state: started
        enabled: true
```

In Semaphore UI, I can now create my first `Task Template` for Ansible playbook. I give it a name, the playbook path (from the root folder of the repo), the repository and its branch:
![Nouveau template de tâche Ansible dans Semaphore UI](img/semaphore-create-new-ansible-task-template.png)

Time to launch the playbook! In the task templates list, I click on the ▶️ button:
![Lancement du template de tâche Ansible dans Semaphore UI](img/semaphore-run-test-playbook.png)

The playbook launches and I can follow the output in real time:
![Semaphore UI Ansible task output](img/semaphore-ui-ansible-task-output.png)

I can also review previous runs:
![Liste des exécutions de tâches dans Semaphore UI](img/semaphore-ui-task-template-run-list.png)


✅ Finally I can confirm the job is done by checking the URL on port 80 (http):
![Test de l'URL après application du playbook sur les hôtes](img/semaphore-ui-test-nginx-page-playbook.png)

Managing Ansible playbooks in Semaphore UI is pretty simple and really convenient. The interface is really sleek.

There are also a lot of customization available when setting the task template up. I can use variables in a survey, specify limit or tags. I really like it.

---
## Deploy with Terraform

While running Ansible playbooks was easy out of the box, this was a bit different to deploy with Terraform on Proxmox VE. Before starting, I destroy the 3 VMs deployed earlier.

Previously from the CLI, I was interacting on Terraform with the Proxmox cluster using a SSH key. I was not able to put it to work from Semaphore UI. I had to use a username with a password instead.

I told myself it was a good opportunity to use Ansible to create a dedicated Proxmox user. My first run failed with:
```plaintext
Unable to encrypt nor hash, passlib must be installed. No module named 'passlib'
```

This is apparently a known issue with Semaphore’s Python environment. As a workaround, I installed `passlib` directly in the container:
```bash
docker exec -it semaphore_ui pip install passlib
```

With that in place, the playbook succeeded and I could create the user:
```yaml
---
- name: Create Terraform local user for Proxmox
  hosts: nodes
  become: true
  tasks:

    - name: Create terraform user
      ansible.builtin.user:
        name: "{{ terraform_user }}"
        password: "{{ terraform_password | password_hash('sha512') }}"
        shell: /bin/bash

    - name: Create sudoers file for terraform user
      ansible.builtin.copy:
        dest: /etc/sudoers.d/{{ terraform_user }}
        mode: '0440'
        content: |
          {{ terraform_user }} ALL=(root) NOPASSWD: /sbin/pvesm
          {{ terraform_user }} ALL=(root) NOPASSWD: /sbin/qm
          {{ terraform_user }} ALL=(root) NOPASSWD: /usr/bin/tee /var/lib/vz/*
```

Next I create a variable group `pve_vm`. A variable group let me define multiple variables and secrets together:
![Nouveau groupe de variables dans Semaphore UI](img/semaphore-ui-create-variable-group.png)

Then I create a new task template, this time with the kind Terraform Code. I give it a name, the path of the terraform [project](https://github.com/Vezpi/Homelab/tree/main/terraform/projects/semaphore-vms), a workspace, the repository along with its branch and. the variable group:
![Nouveau template de tâche Terraform dans Semaphore UI](img/semaphore-task-template-terraform.png)

Running the template gives me some additional options related to Terraform:
![Options d'exécution Terraform dans Semaphore UI](img/semaphore-running-terraform-code-options.png)

After the Terraform plan, I'm proposed to apply, cancel or stop:
![Plan Terraform dans Semaphore UI](img/semaphore-terraform-task-working.png)

Finally after hitting ✅ to apply, I could watch Terraform build the VMs, just like using the CLI. At the end, the VMs were successfully deployed on Proxmox:
![Déploiement Terraform terminé dans Semaphore UI](img/semaphore-ui-deploy-with-terraform.png)

---
## Conclusion

That's it for my Semaphore UI tests, I hope this could help you to see what you can do with it.

Overall, the interface is clean and pleasant to use. I can definitely see myself scheduling Ansible playbooks with it, like the OPNsense updates I mentioned in the intro.

For Terraform, I’ll probably use it to spin up short-lived VMs for tests. I’d love to use the HTTP backend for tfstate, but that requires the Pro version.

To conclude, Semaphore UI is a great tool, intuitive, good-looking, and practical. Nice work from the project!