Prune

Pruning with Kamal

You are an expert in deploying applications with Kamal. Your goal is to keep servers from filling up with old container and image layers — by understanding what Kamal prunes automatically, running a manual prune when you need to reclaim space, and tuning how many old releases Kamal keeps.

Before You Start

Read the project's Kamal config before asking the user questions — it tells you how many releases this app retains.

• config/deploy.yml — the default config file. Look for a retain_containers: setting; if it's absent, Kamal uses the default.
• config/deploy.<destination>.yml — destination-specific config (for example config/deploy.staging.yml).

What Kamal Prunes

Kamal keeps the last 5 deployed containers and the images they are using. Pruning deletes all older containers and images.

This retention is what makes pruning safe: the most recent releases stay on your servers, so you can still inspect or roll back to them, while stale layers that nothing references get cleaned away to reclaim disk.

When Pruning Happens

You usually don't run pruning by hand. It is wired into the deploy flow:

• kamal deploy prunes unused images and stopped containers at the end of every deploy, so servers don't fill up over time.
• kamal redeploy skips pruning (along with bootstrapping, starting kamal-proxy, and registry login) to be faster.

Run a manual prune when you've been redeploying repeatedly, are running low on disk, or want to clean up on demand between deploys.

Walk-Through: Pruning Manually

Step 1 — Decide what to reclaim

• Old stopped containers and unused images together → kamal prune all
• Only unused images → kamal prune images
• Only old stopped containers → kamal prune containers

Step 2 — Run the prune

# Most common: clean up both unused images and stopped containers
kamal prune all

Kamal keeps the last 5 deployed containers and the images they use, so this only removes layers older than your retention window.

Step 3 — Target images or containers individually

# Remove only unused images
kamal prune images

# Remove only stopped containers, keeping the last n (default 5)
kamal prune containers

Prune Subcommands

kamal prune is a command group. Running it on its own lists the available subcommands rather than pruning anything — call a subcommand to act:

For the full subcommand reference and how pruning ties into kamal deploy, see references/prune-commands.md.

Controlling Retention with retain_containers

The number of old containers and images Kamal keeps is configurable. Set retain_containers in config/deploy.yml:

# Keep only the last 3 old containers and images instead of the default 5
retain_containers: 3

Lower it to reclaim disk more aggressively; raise it if you want more previous releases available on the servers. This is the n that kamal prune containers honors ("except the last n").

Quick Reference

Related Skills

• deploy: For running kamal deploy (which prunes unused images and stopped containers at the end) and kamal redeploy (which skips pruning).
• app: For inspecting and managing already-running app containers with the kamal app subcommands before or after you prune.