kamal rollback
You can rollback a deployment with kamal rollback.
If you’ve discovered a bad deploy, you can quickly rollback to a previous image. You can see what old containers are available for rollback by running kamal app containers -q. It’ll give you a presentation similar to kamal app details, but include all the old containers as well.
App Host: 192.168.0.1
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
1d3c91ed1f51 registry.digitalocean.com/user/app:6ef8a6a84c525b123c5245345a8483f86d05a123 "/rails/bin/docker-e..." 19 minutes ago Up 19 minutes 3000/tcp chat-6ef8a6a84c525b123c5245345a8483f86d05a123
539f26b28369 registry.digitalocean.com/user/app:e5d9d7c2b898289dfbc5f7f1334140d984eedae4 "/rails/bin/docker-e..." 31 minutes ago Exited (1) 27 minutes ago chat-e5d9d7c2b898289dfbc5f7f1334140d984eedae4
App Host: 192.168.0.2
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
badb1aa51db4 registry.digitalocean.com/user/app:6ef8a6a84c525b123c5245345a8483f86d05a123 "/rails/bin/docker-e..." 19 minutes ago Up 19 minutes 3000/tcp chat-6ef8a6a84c525b123c5245345a8483f86d05a123
6f170d1172ae registry.digitalocean.com/user/app:e5d9d7c2b898289dfbc5f7f1334140d984eedae4 "/rails/bin/docker-e..." 31 minutes ago Exited (1) 27 minutes ago chat-e5d9d7c2b898289dfbc5f7f1334140d984eedae4
From the example above, we can see that e5d9d7c2b898289dfbc5f7f1334140d984eedae4 was the last version, so it’s available as a rollback target. We can perform this rollback by running kamal rollback e5d9d7c2b898289dfbc5f7f1334140d984eedae4.
That’ll stop 6ef8a6a84c525b123c5245345a8483f86d05a123 and then start a new container running the same image as e5d9d7c2b898289dfbc5f7f1334140d984eedae4. Nothing needs to be downloaded from the registry.
Note: By default, old containers are pruned after 3 days when you run kamal deploy.