Helm is a kubernetes(k8s) package manager and it enables downloading k8s charts and installing them in k8s cluster. Charts are configured with default values, which can be customized before installation.
helm inspect [chart] shows the Chart.yaml and values.yaml content of a
given chart. The configurations are stored in values.yaml and
heml inspect values [chart] shows only the content of values.yaml.
values.yaml of mariadb chart:
---
image: bitnami/mariadb:10.1.23-r2
## Specify an imagePullPolicy (Required)
imagePullPolicy: IfNotPresent
## Specify password for root user
# mariadbRootPassword:
## Create a database user
# mariadbUser:
# mariadbPassword:
## Create a database
# mariadbDatabase:
...Customizing the Chart Before Installing
describes how these configurations can be customized by passing a file name or
--set flags. But this would not preview the set configurations and install
immediately. Or fail if there were any unexpected values found in the
configuration.
To preview the customized configuration, helm dry-run and debug execution modes can be coupled. This shows the resulting configuration and since it’s a dry-run, it won’t result in actual installation.
$ helm install --dry-run --debug stable/mariadb --set mariadbDatabase=somedbname
...
NAME: goodly-quoll
REVISION: 1
RELEASED: Wed Jul 26 22:31:22 2017
CHART: mariadb-0.6.3
USER-SUPPLIED VALUES:
mariadbDatabase: somedbname
COMPUTED VALUES:
image: bitnami/mariadb:10.1.23-r2
imagePullPolicy: IfNotPresent
mariadbDatabase: somedbname
...
NOTE: dry-run result doesn’t mean the configuration is correct. It’s just a preview of the passed configuration parsed by helm. If there’s any misconfiguration, the installation would fail.