Image garbage collection relies on disk usage as reported by cAdvisor on the node to decide which images to remove from the node.
The policy for image garbage collection is based on two conditions:
-
The percent of disk usage (expressed as an integer) which triggers image garbage collection. The default is 85.
-
The percent of disk usage (expressed as an integer) to which image garbage collection attempts to free. Default is 80.
For image garbage collection, you can modify any of the following variables using a Custom Resource.
| Setting | Description |
|---|---|
|
The minimum age for an unused image before the image is removed by garbage collection. The default is 2m. |
|
The percent of disk usage, expressed as an integer, which triggers image garbage collection. The default is 85. |
|
The percent of disk usage, expressed as an integer, to which image garbage collection attempts to free. The default is 80. |
Two lists of images are retrieved in each garbage collector run:
-
A list of images currently running in at least one pod.
-
A list of images available on a host.
As new containers are run, new images appear. All images are marked with a time stamp. If the image is running (the first list above) or is newly detected (the second list above), it is marked with the current time. The remaining images are already marked from the previous spins. All images are then sorted by the time stamp.
Once the collection starts, the oldest images get deleted first until the stopping criterion is met.