Container runtimes
From 1.15 onwards, Charmed Kubernetes uses containerd as part of a pluggable architecture for container runtimes. This change has been demonstrated to increase performance, and also provides scope for using different runtimes on a case-by case basis.
Upstream support for the Docker container runtime was removed in the 1.24 release. Thus, the
docker subordinate charm will no longer function from Charmed Kubernetes 1.24 onwards.
Configuring containerd
Settings which require additional explanation are described below.
| name | type | Default | Description |
|---|---|---|---|
| custom_registries | string | [] | See notes |
| disable-juju-proxy | boolean | False | Ignore juju-http(s) proxy settings on this charm. If set to true, all juju https proxy settings will be ignored |
| enable-cgroups | boolean | False | Enable GRUB cgroup overrides cgroup_enable=memory swapaccount=1. WARNING changing this option will reboot the host - use with caution on production services. |
| gpu_driver | string | auto | Override GPU driver installation. Options are “auto”, “nvidia”, “none”. |
| http_proxy | string | URL to use for HTTP_PROXY to be used by Containerd. Useful in egress-filtered environments where a proxy is the only option for accessing the registry to pull images. | |
| https_proxy | string | URL to use for HTTPS_PROXY to be used by Containerd. Useful in egress-filtered environments where a proxy is the only option for accessing the registry to pull images. | |
| no_proxy | string | See notes | |
| runtime | string | auto | Set a custom containerd runtime. Set “auto” to select based on hardware. |
| shim | string | containerd-shim | Set a custom containerd shim. |
custom_registries
Registry credentials. Setting this config allows Kubelet to pull images from registries where auth is required.
The value for this config must be a JSON array of credential objects, like this:
[{"url": "https://my.registry:port", "username": "user", "password": "pass"}]
no_proxy
Comma-separated list of destinations (either domain names or IP addresses) which should be accessed directly, rather than through the proxy defined in http_proxy or https_proxy. Must be less than 2023 characters long.
Checking the current configuration
To check the current configuration settings for containerd, run the command:
juju config containerd
Setting a config option
To set an option, simply run the config command with an additional <key>=<value> argument. For example, to explicitly turn off the nvidia driver:
juju config containerd gpu_driver=none
Migrating to containerd
If you are upgrading from a version of Charmed Kubernetes that uses the docker
subordinate charm for the container runtime, transition to containerd by following
the steps outlined in this section of the upgrade notes.
See the guide to contributing or discuss these docs in our public Mattermost channel.