Accessories #

Accessories can be booted on a single host, a list of hosts, or on specific roles. The hosts do not need to be defined in the Kamal servers configuration.

Accessories are managed separately from the main service - they are not updated when you deploy and they do not have zero-downtime deployments.

Run kamal accessory boot <accessory> to boot an accessory. See kamal accessory --help for more information.

Configuring accessories #

First define the accessory in the accessories

accessories:
  mysql:

Service name #

This is used in the service label and defaults to <service>-<accessory> where <service> is the main service name from the root configuration

    service: mysql

Image #

The Docker image to use, prefix with a registry if not using Docker hub

    image: mysql:8.0

Accessory hosts #

Specify one of host, hosts or roles

    host: mysql-db1
    hosts:
      - mysql-db1
      - mysql-db2
    roles:
      - mysql

Custom command #

You can set a custom command to run in the container, if you do not want to use the default

    cmd: "bin/mysqld"

Port mappings #

See https://docs.docker.com/network/, especially note the warning about the security implications of exposing ports publicly.

    port: "127.0.0.1:3306:3306"

Labels #

    labels:
      app: myapp

Options #

These are passed to the Docker run command in the form --<name> <value>

    options:
      restart: always
      cpus: 2

Environment variables #

See Environment variables for more information

    env:
      ...

Copying files #

You can specify files to mount into the container. The format is local:remote where local is the path to the file on the local machine and remote is the path to the file in the container.

They will be uploaded from the local repo to the host and then mounted.

ERB files will be evaluated before being copied.

    files:
      - config/my.cnf.erb:/etc/mysql/my.cnf
      - config/myoptions.cnf:/etc/mysql/myoptions.cnf

Directories #

You can specify directories to mount into the container. They will be created on the host before being mounted

    directories:
      - mysql-logs:/var/log/mysql

Volumes #

Any other volumes to mount, in addition to the files and directories. They are not created or copied before mounting

    volumes:
      - /path/to/mysql-logs:/var/log/mysql