Skip to main content
Version: 0.9


Acorn image

When you install acorn, it will launch several workloads in your cluster, including an api-server and controller. By default, these workloads will use the image. You can customize this image by setting the --image option. This is useful if you are installing acorn in an environment where you are required to pull images from a private registry.

TLS via Let's Encrypt

When you launch an acorn and it has published ports, acorn will generate a unique URL for accessing it, like so:

$ acorn run -P

$ acorn ps
little-snowflake eab5f8c77bd6 1 1 6m2s ago => webapp:80 OK

By default, endpoints are http. To have acorn automatically generate a Let's Encrypt certificate and secure your endpoints, you can enable acorn's Let's Encrypt integration like this:

acorn install --lets-encrypt enabled

If you add this flag, you'll be prompted during install to agree to Let's Encrypt's Terms of Service and supply an email. You can supply these as flags too:

acorn install --lets-encrypt enabled --lets-encrypt-tos-agree=true --lets-encrypt-email <your email>

Let's Encrypt integration is only useful if you are running a non-local Kubernetes cluster. If you are running acorn on a local cluster such as Docker Desktop, Rancher Desktop, or minikube, enabling Let's Encrypt will have no effect. We don't issue certificates for the domains that are used in this scenario.

Endpoint domain names

Acorn provides several installation options for controlling the domain name used to generate endpoints. These are outlined in detail on our networking page.

Custom CA bundle

Acorn allows a user to provide a custom certificate authority (CA) bundle so that users can add their own private CA that acorn will trust. The most common use case is for acorn to trust an internal image registry that is signed by a private CA.

To do so, you will need to go through the following steps:

  1. Provide your CA certificate chain in the following secret.
kubectl -n acorn-image-system create secret generic cabundle --from-file=ca-certificates.crt=/path/to/your/ca-certificates.crt

kubectl -n acorn-system create secret generic cabundle --from-file=ca-certificates.crt=/path/to/your/ca-certificates.crt

You must provide the full CA certificate chain as it will override existing CA certificates in acorn control plane.

  1. Install acorn with the following option
acorn install --use-custom-ca-bundle

Ingress class name

Acorn requires an ingress controller to function properly. If your cluster has more than one ingress controller or if it has one but it isn't set as the default, you can explicitly set the ingress class using --ingress-class-name.


There are two install flags for interacting memory: --workload-memory-default and --workload-memory-maximum. Their values can both be viewed by running acorn info.

Check out the memory reference documentation for more information.


This flag is responsible for setting the memory amount that will get defaulted to should no other value be found.

acorn install --workload-memory-default 512Mi

Running the above will set all Acorns on the cluster (current and future) to use 512Mi as their default memory.


This flag sets a maximum that when exceeded prevents the offending Acorn from being installed.

acorn install --workload-memory-maximum 1Gi

This will set it so all Acorns on this cluster will be unable to install should they exceed 1Gi of memory.

Ignoring user-defined labels and annotations

There are situations where you may not want a user to be able to label or annotate the objects created by Acorn in the workload cluster. For such circumstances, the installation flag --ignore-user-labels-and-annotations exists. If this flag is passed to acorn install, then, except for the metadata scope, labels and annotations defined by users in their Acorns will be ignored when creating objects. No error nor warning will be produced.

If this is too restrictive, and you would like to allow certain user-defined labels and annotations to propagate to the Kubernetes objects then you can use the --allow-user-label and allow-user-annotation installation flags. These flags take a comma-delimited list of label/annotation keys that are allowed to propagate. You can also specify the flags multiple times and the values will be concatenated to create the final list. If the --ignore-user-labels-and-annotations is not supplied or is false, then these flags have no effect.

Note that in order to allow propagation of user-defined labels and annotations on an Acorn installation that previous disallowed it, one must pass --ignore-user-labels-and-annotations=false to acorn install.

Manually managing volume classes

The default installation of Acorn will automatically create and sync any storage classes in the cluster to volume classes. That means that when a storage class is created or deleted, the corresponding volume class will also be created or deleted. Additionally, the default storage class in the cluster will also become the default volume class. An admin could edit these generated volume classes to set the fields on them (like min/max/default size) and those updates will be maintained. These generated volume classes will be available to every user in the cluster.

If an admin would rather manually manage the volume classes and not have these generated ones, then the --manage-volume-classes installation flag is available. The generated volume classes are not generated if this flag is used, and are deleted when the flag is set on an existing Acorn installation. If the flag is again switched off with --manage-volume-classes=false, then the volume classes will be generated again.

Kubernetes NetworkPolicies

Acorn can automatically create and manage Kubernetes NetworkPolicies to isolate Acorn projects on the network level. This behavior can be enabled by passing --network-policies=true to acorn install, and can later be disabled by passing --network-policies=false.

When NetworkPolicies are enabled, Acorn workloads that publish ports that use HTTP will be allowed to receive traffic from internal (other pods in the cluster) and external (through the cluster's ingress) sources. To secure this further, you can require all traffic to Acorn workloads flow through your ingress by specifying the --ingress-controller-namespace parameter during installation.


Acorn workloads that publish ports that use TCP will be allowed to receive traffic from any source, whether it comes from outside or inside of the cluster.

To allow traffic from a specific namespace to all Acorn apps in the cluster, use --allow-traffic-from-namespace=<namespace>. This is useful if there is a monitoring namespace, for example, that needs to be able to connect to all the pods created by Acorn in order to scrape metrics.

Working with external LoadBalancer controllers

If you are using an external LoadBalancer controller that requires annotations on LoadBalancer Services to operate, such as the aws-load-balancer-controller, you can pass the --service-lb-annotation flag to acorn install. This will cause Acorn to add the specified annotations to all LoadBalancer Services it creates. The value of the flag should be a comma-separated list of key-value pairs, where the key is the annotation name and the value is the annotation value. For example:

acorn install --service-lb-annotation,,

For readability, you can also pass the flag multiple times, and the values will be concatenated. For example:

acorn install \
--service-lb-annotation \
--service-lb-annotation \
--service-lb-annotation \

Lastly, you can unset the annotations defined by the --service-lb-annotation flag by passing an empty string to the flag. For example:

acorn install --service-lb-annotation ""

These annotations get added before the the LoadBalancer Service is created which is a requisite for some LoadBalancer controllers to work properly, like the aws-load-balancer-controller.

Changing install options

If you want to change your installation options after the initial installation, just rerun acorn install with the new options. This will update the existing install dynamically.

For strings array flags, you can reset the slice to empty by pass empty string "". For example:

acorn install --propagate-project-annotation ""

Install Profiles

When you are installing Acorn, you can specify a profile to use. A profile is a set of installation flag defaults that are pre-defined. You can see the list of available profiles by running acorn install --help. The default profile is default, and it is used if no profile is specified.


Once a profile is set, this will set new default values based on the profile. Any default values previously used will be switched to the new profile defaults. However, any install flags that were or are specified will still be respected.