Start shipping →

Answers · Deploying

How do I point a domain at a server running Kamal?

Create an A record for the apex pointing at the server's public IPv4 address, and a CNAME for www pointing at the apex. Set the same hostname in the proxy section of config/deploy.yml and redeploy. Kamal's proxy requests a certificate on the first request to that host, so HTTPS starts working within a minute of DNS resolving.

Updated · 2 min read

The records

Type Name Value
A @ your server's IPv4 address
CNAME www yourdomain.com

Keep the TTL low, around 300 seconds, until you are confident. You can raise it later, and a low TTL means a mistake costs five minutes rather than a day.

dig +short yourdomain.com
curl -sI https://yourdomain.com/up | head -1

Tell Kamal which host it is serving

The proxy needs the hostname to request a certificate for it. That lives in config/deploy.yml:

proxy:
  ssl: true
  host: yourdomain.com

Redeploy after changing it. The certificate is requested on the first request that arrives for that host, so the sequence is: DNS resolves, a request lands, the certificate is issued, and the second request is already on HTTPS.

Also set APP_HOST

This one is silent when you miss it. Rails builds absolute URLs for emails, canonical tags and the sitemap from APP_HOST, not from the request. Without it, a magic-code email links to localhost:3000 and the link does not work for anyone.

bin/kamal app exec 'bin/rails runner "puts Rails.application.config.x.app_host"'

The two things that make this look broken when it is not

DNS caching. Your machine may hold the old answer for as long as the previous TTL. dig against a public resolver directly, such as dig @1.1.1.1 yourdomain.com, tells you what the world sees rather than what your laptop remembers.

A proxy in front. If you put Cloudflare or another CDN ahead of the server, it terminates TLS itself and Kamal's certificate request may never see a request. That setup needs its own configuration, covered in Edge and DNS Setup.

Related questions

How do I run a second Rails app on the same server?

Give the second app its own service name and its own host in config/deploy.yml. Kamal's proxy routes by hostname, so two apps share port 443 without conflict. What collides is anything pinned to a fixed host port, and the database volume path, which must differ or the two apps will share one SQLite file.

Can I run SQLite in production for a Rails app?

Yes, for one server. Rails 8 ships SQLite configured for production use, and One Shot runs on it: the database is a file on a mounted volume, backups are a file copy, and there is no second service to operate. The limit is real though. Two application servers cannot write to the same SQLite file, so horizontal scaling is where it stops.

How do I back up a SQLite database on a live server?

Run sqlite3 storage/production.sqlite3 ".backup /tmp/out.sqlite3" inside the container, then copy the result off the host. The .backup command takes a consistent snapshot while writes continue; a plain cp of a live database gives you a file that looks fine and fails on restore. Store it somewhere the server cannot reach.