imagePullPolicy
Always
總是拉取 pull
IfNotPresent
默認值,本地有則使用本地鏡像,不拉取
imagePullPolicy: IfNotPresent
Never
只使用本地鏡像，從不拉取
Pre-pulling Images
Note: If you are running on Google Kubernetes Engine, there will already be a .dockercfg on each node with credentials for Google Container Registry. You cannot use this approach.
Note: This approach is suitable if you can control node configuration. It will not work reliably on GCE, and any other cloud provider that does automatic node replacement.
By default, the kubelet will try to pull each image from the specified registry. However, if the imagePullPolicy property of the container is set to IfNotPresent or Never, then a local image is used (preferentially or exclusively, respectively).
If you want to rely on pre-pulled images as a substitute for registry authentication, you must ensure all nodes in the cluster have the same pre-pulled images.
This can be used to preload certain images for speed or as an alternative to authenticating to a private registry.
All pods will have read access to any pre-pulled images
