How to Deploy Web Apps Using Kamal in 2023: Effective Containerized Application Deployment

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Nov 16, 2023

Ariffud M.

10min Read

 Effective Containerized Application Deployment

Deploying a containerized web exertion tin often look daunting. Kamal is simply a instrumentality designed to streamline and simplify nan deployment of web apps, making your workflow much businesslike and reliable.

In this article, you’ll study really to deploy web apps utilizing Kamal connected a virtual backstage server (VPS) environment. We’ll besides supply respective champion practices to heighten your exertion deployment process.

By nan extremity of this guide, you’ll beryllium well-equipped to leverage nan powerfulness of Kamal for your projects. Let’s get started.

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What Is Kamal?

Kamal is simply a deployment instrumentality that facilitates nan businesslike rollout of web apps. It integrates basal services and operations into a cohesive workflow, making web app deployment pinch Kamal streamlined and little error-prone.

Designed to negociate and automate nan deployment of web applications, Kamal reduces nan complexity often associated pinch manual server and work management. It allows developers to attraction connected building and updating their web apps without nan overhead of deployment logistics.

Kamal supports deployments ranging from a bare metallic server to a azygous VM. It offers zero-downtime deployments, rolling restarts, plus bridging, distant builds, and broad accessory work management.

With Kamal, you tin effortlessly deploy web apps, configure servers, negociate databases, and grip postulation balancing. This instrumentality supports various environments, making it versatile for deploying web applications crossed different platforms.

Why Use Kamal for Web App Deployment?

Kamal charismatic homepage

Choosing Kamal for your web app deployment offers respective benefits for developers and businesses. Here’s what makes Kamal guidelines out:

  • Simplicity – Kamal’s straightforward attack to deployment cuts done nan often steep learning curve associated pinch different deployment tools. It simplifies nan process, enabling exertion deployment pinch conscionable a fewer Linux commands.
  • Automation – Kamal automation for deployments streamlines your workflows. From updates to scaling, Kamal automates these tasks, ensuring they are completed quickly and consistently. This intends little clip connected manual processes and much connected development.
  • Reliability – pinch Kamal, you tin expect unchangeable releases. Its system deployment process minimizes nan errors that tin hap pinch manual deployments, ensuring your web exertion runs smoothly and reliably.
  • Suitability – Kamal is exceptionally compatible pinch Linux VPS environments. Its alignment pinch Linux servers intends you tin harness nan afloat imaginable and elasticity of deploying applications connected Linux VPS hosting.

How to Deploy Web Apps Using Kamal

In this section, you’ll study really to usage Kamal to streamline your web app deployment process.

1. Prepare for Deployment

Whether utilizing a section instrumentality aliases a virtual server, preparing nan prerequisites ensures a soft web exertion deployment pinch Kamal. In this example, we’ll usage Hostinger’s VPS hosting to group up your situation for deploying a web app.

Hostinger’s VPS offers a reliable server that sets nan shape for your deployment needs. It provides top-notch information measures, easy scalability to turn alongside your application, and an AI adjunct to simplify your improvement and deployment processes.

After preparing your VPS, access your server pinch PuTTY aliases immoderate different SSH client. Then, update your Linux packages pinch nan pursuing SSH commands:

sudo apt-get update && sudo apt-get upgrade

Next, group up nan package situation required by your web app, which whitethorn see installing a web server for illustration Apache aliases NGINX and mounting up a database specified arsenic MySQL aliases PostgreSQL. It’s besides captious to unafraid your server pinch firewalls and SSH keys for safe access.

If you are processing a Rails app, guarantee Ruby connected Rails is installed. Otherwise, you tin install Docker and negociate containers for your application.

2. Install and Deploy pinch Kamal

Once your situation is ready, proceed pinch nan Kamal installation. For those pinch a Ruby environment, instal Kamal globally connected your Linux VPS pinch nan pursuing command:

gem instal kamal

This makes Kamal accessible from immoderate directory wrong your server.

If you for illustration containerization successful Kamal deployments, propulsion nan Docker image and group an othername successful your ammunition config file. This allows you to usage Kamal commands without installing nan limitations connected your server.

Next, navigate to nan config directory and unfastened nan deploy.yml file. Here, you tin specify specifications specified arsenic deployment stages, nationalist IP addresses, and nan repository URL for type power pinch Kamal.

Your deploy.yml record will besides see registry details. If you’re utilizing Docker Hub, you won’t request to specify a server because it’s nan default.

Here’s a basal illustration of what nan deploy.yml contented mightiness include:

# Your web app name. Used to uniquely configure containers. service: hey # Your image big aliases instrumentality image name image: 37s/hey servers: - - registry: # The instrumentality registry server, if you're not utilizing Docker Hub # server: / ... username: registry-user-name password: secure: KAMAL_REGISTRY_PASSWORD env: secret: secure: RAILS_MASTER_KEY #Configure a civilization healthcheck healthcheck: path: /healthz port: 4000 max_attempts: 7 interval: 20s

Remember to support your credentials unafraid by replacing KAMAL_REGISTRY_PASSWORD pinch your Docker registry entree token.

With your config record group up, it’s clip to commencement nan deployment process. For first deployment, run:

kamal setup

This prepares your servers by creating directories, mounting permissions, and performing different required tasks.

For consequent deployments, use:

kamal deploy

This bid executes nan tasks outlined successful your deploy.yml file, specified arsenic codification updates, migrations, and work restarts.

3. Push Environment Files

To efficaciously deploy your web app utilizing Kamal, it’s captious to negociate your situation files meticulously. These files incorporate situation variables captious for configuring your exertion crossed various development, testing, and accumulation settings.

For information reasons, your application’s ENV files should ne'er beryllium included successful type control. Instead, leverage Kamal’s robust situation guidance features to transportation these files to your server securely.

Start by securing your situation record successful a safe retention location. Consider utilizing Hostinger’s VPS to reliably negociate your application’s situation variables, ensuring they are securely applied and maintained consistently passim deployment.

Next, utilize nan kamal env push bid to transportation nan record to your server securely.

Whenever you adhd caller aliases modify existing situation variables successful your ENV file, retrieve to push these updates to your distant servers utilizing kamal env push. Before executing nan kamal deploy command, complete this measurement to guarantee that your deployment process incorporates nan updated variables into your app’s container.

These procedures are captious for adequately operating Docker containers and services, arsenic they trust connected nan correct configuration settings provided by nan situation variables.

4. Run Commands connected Servers

To simplify your web exertion management, Kamal provides a user-friendly characteristic that allows you to execute commands crossed your server infrastructure efficiently.

For instance, to tally a bid connected each your servers to cheque nan Ruby version, you would use:

kamal app exec 'ruby -v'

The output will corroborate nan Ruby type connected each app host, for example:

App Host: ruby 3.1.3p185 (2022-11-24 revision 1a6b16756e) [x86_64-linux] App Host: ruby 3.1.3p185 (2022-11-24 revision 1a6b16756e) [x86_64-linux]

To target only nan superior server, nan bid would be:

kamal app exec --primary 'cat .ruby-version'

If you request to tally a Rails-related bid crossed each servers, specified arsenic checking nan Rails situation setup, you will input nan following:

kamal app exec 'bin/rails about'

The output should look for illustration this:

App Host: About your application's environment Rails version: 7.1.0.alpha Ruby version: ruby 3.1.3p185 (2022-11-24 revision 1a6b16756e) [x86_64-linux] RubyGems version: 3.3.26 Rack version: 2.2.5 Middleware: ActionDispatch::HostAuthorization, Rack::Sendfile, ActionDispatch::Static, ActionDispatch::Executor, Rack::Runtime, Rack::MethodOverride, ActionDispatch::RequestId, ActionDispatch::RemoteIp, Rails::Rack::Logger, ActionDispatch::ShowExceptions, Action Dispatch::DebugExceptions, Action Dispatch::Callbacks, Action Dispatch::Cookies, Action Dispatch::Session::CookieStore, Action Dispatch::Flash, Action Dispatch::ContentSecurityPolicy::Middleware, Action Dispatch::PermissionsPolicy::Middleware, Rack::Head, Rack::ConditionalGet, Rack::ETag, Rack::TempfileReaper Application root: /rails Environment: production Database adapter: sqlite3 Database schema version: 20221231233303

For much interactive tasks for illustration launching a Rails console aliases a bash session, Kamal simplifies nan process. Just execute nan pursuing commands to commencement a bash convention successful either a caller app image instrumentality aliases nan presently moving Docker container:

# New instrumentality bash session kamal app exec -i bash # Reuse nan existent instrumentality for bash session kamal app exec -i --reuse bash # New instrumentality Rails console kamal app exec -i 'bin/rails console'

5. Check Server State pinch Kamal Details

Understanding nan authorities of your servers is important for maintaining their wellness and ensuring that your applications tally smoothly. Kamal provides an businesslike measurement to show this done nan details command.

Executing kamal details gives you a snapshot of your containers, their status, and really they are performing. Here’s what you’ll typically see:

For Traefik containers:

Traefik Host: CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS 6195b2a28c81 traefik "/…" 30 minutes agone Up 19 minutes>80/tcp...

For your exertion containers:

App Host: CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS badb1aa51db3 registry.domain.tld/... "/rails/bin/…" 13 minutes agone Up 13 minutes 3000/tcp

This output lets you quickly verify that containers are up and moving and that nan ports are correctly mapped, indicating a patient server state.

For a much focused inspection, you tin constrictive nan specifications to app-specific aliases Traefik-specific containers utilizing kamal app details aliases kamal traefik details, respectively.

These targeted commands supply nonstop entree to logs and instrumentality specifics, streamlining nan process of managing situation configurations and simplifying correction handling successful Kamal deployments.

6. Rollback Deployments

When a deployment doesn’t spell arsenic planned, Kamal provides a elemental rollback process. It involves reactivating a antecedently unchangeable Docker container. To negociate a speedy and businesslike rollback, travel these steps:

First, place nan aged containers disposable utilizing nan kamal app containers command. This will database some progressive and inactive containers. Look for nan past progressive instrumentality by its image tag aliases ID earlier nan grounded deployment.

For example, you mightiness spot an output showing:

App Host: CONTAINER ID IMAGE COMMAND STATUS 1d3c91ed1f51 [previous_image] "/rails/bin/docker-e…" Up 19 minutes 539f26b28369 [failed_image] "/rails/bin/docker-e…" Exited (1) 27 minutes ago

To rollback, execute kamal rollback [previous_image_tag]. Kamal will extremity nan existent problematic instrumentality and restart nan past unchangeable one. With nan erstwhile instrumentality already connected nan host, nan rollback happens quickly without pulling from nan registry again.

Note that aged containers are automatically purged aft 3 days pursuing a caller kamal deploy, truthful it’s advisable to corroborate nan occurrence of your deployment wrong this timeframe to clasp nan action for a swift rollback.

It’s besides basal to guarantee you person nan due backup and betterment pinch Kamal to safeguard against unforeseen issues. Hostinger’s VPS hosting includes automated backups, seamlessly enhancing your rollback capabilities.

7. Clean Up Servers pinch Kamal Remove

Managing server abstraction and capacity involves removing unused applications. With Kamal, cleaning up your server is straightforward. When deleting an full application, execute nan kamal remove command.

Kamal will past region each components associated pinch nan exertion connected nan server, including stopping and removing Docker containers, erasing immoderate Docker image, and clearing immoderate associated registry sessions.

This bid is useful to guarantee your server remains uncluttered and performs optimally. However, it’s basal to usage this characteristic pinch caution. Before moving kamal remove, guarantee you person backups of immoderate information you wish to keep.

8. Reboot Traefik

When managing your server’s reverse proxy and load balancer, location whitethorn beryllium occasions erstwhile you request to reboot Traefik, nan work that routes your HTTP traffic. This request typically arises aft updates to Traefik’s arguments aliases labels, necessitating a reboot for changes to return effect.

To reboot Traefik utilizing Kamal, utilize nan pursuing command:

kamal traefik reboot

This will restart nan Traefik service, implementing your caller configurations. However, successful a accumulation environment, wherever stableness and uptime are critical, opt for nan rolling reboot feature:

kamal traefik reboot --rolling

A rolling reboot methodically restarts Traefik containers sequentially, ensuring nary downtime and maintaining continuous load-balancing functionality. This safer attack ensures that your web applications stay accessible to users while updates proceed successful nan background.

Best Practices for Deploying Web Applications pinch Kamal

After learning really to deploy your web exertion to a server, let’s research immoderate Kamal deployment champion practices for soft and businesslike web app management.

Automate Your Deployment Workflow

Embracing Kamal automation for deployments transforms repetitive manual tasks into a one-click operation. Kamal’s commands and scripts let you to automate your web applications’ first setup, updates, and ongoing maintenance, making nan deployment process quicker and much reliable by reducing quality error.

Integrating Kamal deployment automation devices wrong CI/CD pipelines further enhances efficiency. These pipelines beforehand continuous betterment and seamless updates, enabling an uninterrupted travel from improvement to deployment.

Hostinger’s VPS hosting is ideally suited to these practices, offering an AI Assistant to streamline book automation for managing and scaling your web applications effortlessly. You tin consult nan Hostinger VPS AI adjunct for instructions connected automating your deployment workflow.

For example, initiate a VPS AI prompt for illustration “How do I automate database server backups utilizing Kamal?”

Our AI adjunct will past supply a broad step-by-step guide. You tin inquire follow-up questions to grow connected each measurement if you request further details. The Hostinger VPS AI adjunct tin besides proviso exertion codification templates to velocity up nan setup process.

Deploy Lock and Safe Concurrent Operations

Managing concurrent operations is basal erstwhile deploying web applications to forestall conflicts and sphere nan integrity of your applications. Kamal facilitates this pinch a deploy fastener feature, a coordination system that allows only 1 deployment astatine a time.

Here’s really to incorporated a deploy fastener into your Kamal deployment strategies:

Before Deployment

Initiate a deploy fastener to preclude overlapping deployment processes utilizing nan bid kamal fastener get -m “Your logic for locking”. This creates a kamal_lock directory connected nan superior server, indicating that a deployment process is underway.

During Deployment

Verify nan fastener position pinch kamal fastener status to find who has initiated nan fastener and for what purpose, arsenic good arsenic which type is being deployed. You mightiness spot an output akin to this:

Locked by: A.N. Other connected 2023-03-24 09:49:03 UTC Version: 77f45c0686811c68989d6576748475a60bf53fc2 Message: Automatic deploy lock

This output helps you enactment informed astir ongoing deployment activities and ensures nary conflicting operations are conducted.

After Successful Deployment

Conclude your deployment by releasing nan deploy fastener pinch kamal fastener release. This action is important for clearing nan situation for early implementations and ensuring continuous deployment operations.

Use Kamal Hooks

Kamal provides a hook strategy that allows developers to execute civilization scripts astatine predefined points successful nan deployment process, offering tailored automation and ensuring nan deployment’s integrity and reliability. They travel successful 4 types:

  • Pre-connect hooks – executed earlier Kamal takes a deploy fastener and earlier connecting to nan distant hosts. These hooks are useful for DNS warming tasks.
  • Pre-build hooks – tally earlier nan build process starts, allowing for pre-build validations for illustration checking for uncommitted changes aliases ensuring continuous integration (CI) has passed.
  • Pre-deploy hooks – triggered correct earlier nan deployment starts, suitable for last checks for illustration verifying CI completion.
  • Post-deploy hooks – activated aft a deploy, redeploy, aliases rollback hook. Post-deploy hooks tin nonstop deployment notifications aliases registry nan caller type pinch an exertion capacity guidance (APM) system.

The scripts successful these hooks person entree to a scope of KAMAL_* situation variables, which supply elaborate discourse astir nan deployment, including timestamps, personification information, type details, and big lists. If immoderate book exits pinch a non-zero status, nan deployment process will beryllium aborted to forestall imaginable errors from propagating.

Here is 1 illustration of creating a post-deploy hook book that sends a deployment notification to a chatbot successful Basecamp utilizing nan KAMAL_* variables:

#!/usr/bin/env bash curl -q -d "content=[My App] ${KAMAL_PERFORMER} Rolled backmost to type ${KAMAL_VERSION}"

This book would station a connection indicating who performed nan rollback and to which version.

In situations wherever hooks are not needed, you tin bypass them by utilizing nan –skip_hooks emblem during deployment commands, which prevents nan execution of these civilization scripts.


Throughout this guide, you’ve discovered what Kamal is, its advantages, and nan steps for deploying web apps utilizing Kamal connected a Linux VPS. You’ve besides learned Kamal deployment tips, specified arsenic workflow automation, securing operations pinch deploy locks, and optimizing processes pinch Kamal hooks.

As you proceed to activity improvements for your web applications, see utilizing Hostinger’s VPS hosting. Our plans statesman astatine conscionable $5.99/month, each packed pinch a suite of features to elevate your success.

These see complimentary real-time snapshots, automatic play backups, and entree to an AI Assistant, each designed to complement your deployment strategy and boost your project’s performance.

Embrace nan spot of Hostinger’s VPS hosting for your Kamal-powered web app deployments. Unleash nan afloat imaginable of your online beingness by clicking nan banner below!

Deploy Web Apps Using Kamal FAQ

This conception will reply nan astir communal questions astir really to deploy web apps utilizing Kamal.

What Are nan Prerequisites for Using Kamal to Deploy Web Apps?

Before deploying pinch Kamal, guarantee your instrumentality has Git installed for type control, SSH entree to your server for unafraid connections, and a Rails app situation pinch nan basal limitations resolved. These prerequisites are important for a seamless Kamal deployment process.

Can I Deploy Different Types of Web Applications With Kamal?

Yes, Kamal tin grip different types of web applications beyond conscionable Rails apps. It provides a elastic deployment strategy suitable for various web exertion frameworks, ensuring developers tin deploy their projects efficaciously sloppy of nan underlying technology.

Is Kamal Suitable for Scaling Web Applications?

Kamal is perfect for scaling web apps arsenic it supports deployment crossed aggregate hosts and integrates pinch a load balancer, basal for postulation distribution and ensuring precocious readiness arsenic your personification guidelines and postulation expand.


The author

Ariffud Muhammad

Ariffud is simply a Technical Content Writer and On-page SEO Specialist who has produced complete 200 pieces of content. In his spare time, he serves arsenic a speaker and mentor for respective events.