The Image layers explorer is an extension for Podman Desktop.
When installed, Podman Desktop displays a new "Files" tab in the Details page of Images.
When you open this tab, the layers of the image are listed. By clicking on a specific layer, you can display the files included in this layer.
Layers are displayed in the order of the operations in a Dockerfile / Containerfile: to illustrate, the first layer is the result of the FROM <image> placed in the first line of the Dockerfile / Containerfile.
Two modes are available for displaying files of a layer:
- normal mode: in this mode, the files displayed are the files that would be available when creating a container based on this image, if the layer stack was finished at this layer.
- layer only: in this mode, the files displayed are the files added or deleted by this layer. The deleted files are displayed in red.
Three sizes are displayed for each layer, for example:
Layer 1
4 MB | 4 MB | 4MB
Layer 2
100 kB | 100 kB | 4.1 MB
Layer 3
0 B | -100 kB | 4 MB
- the first size indicates the size necessary to store the layer at rest (when stored by a registry for example).
- the second size indicates the contribution of the layer in the size of the files deployed in a container.
- the third size indicates the total size of the files deployed in a container.
In the example above:
- the first layer contains several files, for a total of 4 MB. If a container was created at this level, the files would occupy 4 MB in the container.
- the second layer adds a 100 kB file. For a container created at this level, the files would occupy 4.1 MB, and the contribution of this second layer in this size is 100 kB.
- the third layer removes the file introduced by the second layer (which was a 100 kB file). Because removing a file is done by creating an empty file with a specific name, the size of the layer at rest is zero. The total size of files in the created container is 4 MB, and the contribution of this third layer is -100 kB, because it reduces the total size in the container.