If you implement my suggestions about wrapping diskimage.Put(), adding a test case to TestDomainDefinitions will be trivial. I'm ok with e2e as a followup but pls add some minimal coverage, it's easy with Golden Master.

Reviewable status: 0 of 2 approvals obtained (waiting on @jellonek)

docs/configmap-as-files.md, line 1 at r1 (raw file):

# Tuning rootfs of VM using config map as files

Maybe "Adding files from ConfigMaps to the root filesystem" ?

docs/configmap-as-files.md, line 6 at r1 (raw file):

image pointed in `container` part of pod definition by using an user selected
[Config Map](https://kubernetes.io/docs/tasks/configure-pod-container/configure-pod-configmap/)
as a source of data.

Virtlet makes it possible to add a set of files from a ConfigMap to the root filesystem of a VM.

docs/configmap-as-files.md, line 10 at r1 (raw file):

## Usage

Prepare config map:

Create ConfigMap:

docs/configmap-as-files.md, line 15 at r1 (raw file):

then add to pod annotations: VirtletConfigMapAsFiles: sample-data.

then add the following to the pod annotations:

docs/README.md, line 16 at r1 (raw file):

    * [Image Name Translation](image-name-translation.md)
* [Diagnostics](diagnostics.md)
* [Tuning rootfs of VM using config map as files](configmap-as-files.md)

Adding files from ConfigMaps to the root filesystem

pkg/diskimage/diskimage_linux.go, line 96 at r1 (raw file):

}

// Put insert files to image creating all necessary subdirs

// Put adds files to the image, making all the necessary subdirs

pkg/diskimage/diskimage_linux.go, line 97 at r1 (raw file):

// Put insert files to image creating all necessary subdirs
func Put(image string, files map[string][]byte) error {

Please add a placeholder for this function to diskimage_unsupported.go, too.

pkg/diskimage/diskimage_linux.go, line 117 at r1 (raw file):

	}

	// Run the libguestfs back-end.

// Run the libguestfs backend

pkg/diskimage/diskimage_linux.go, line 124 at r1 (raw file):

	// Get the list of devices.  Because we only added one drive
	// above, we expect that this list should contain a single
	// element.

// Get the list of devices. As we've added just one drive above, we
// expect this list to contain just one item.

pkg/diskimage/diskimage_linux.go, line 141 at r1 (raw file):

	}

	// Try to mount fist partition of image as /.

Try to mount the first partition of the image as /

pkg/diskimage/diskimage_linux.go, line 150 at r1 (raw file):

		if len(dir) > 1 {
			// Just in case - try to create directory structure
			// as it can be missing.

// Make sure all the containing directories exist

pkg/libvirttools/extdata.go, line 66 at r1 (raw file):

}

func loadConfigMapAsFilesMap(ns, name string) (map[string][]byte, error) {

loadConfigMapAsFileMap

pkg/libvirttools/persistentroot_volumesource.go, line 96 at r1 (raw file):

	}

	if err := diskimage.Put(v.dmPath(), v.config.ParsedAnnotations.FilesForRootfs); err != nil {

This makes this part of code untestable. Look how volume formatting is done in qcow2_flexvolume.go. You need to add PutFiles() method to virt.StorageVolume interface, then add a method that calls the actual Put() to pkg/virtualization/libvirt_storage.go, and a fake implementation that records the call (with the contents of the files!) to pkg/virt/fake/fake_storage.go.

Another thing, you should probably skip this call altogether if v.config.ParsedAnnotations.FilesForRootfs is empty.

pkg/libvirttools/root_volumesource.go, line 106 at r1 (raw file):

	}

	if err := diskimage.Put(volPath, v.config.ParsedAnnotations.FilesForRootfs); err != nil {

Same as above. Don't add direct call to diskimage here. Also, you should probably skip this call altogether if v.config.ParsedAnnotations.FilesForRootfs is empty.

pkg/metadata/types/annotations.go, line 208 at r1 (raw file):

	}

	if configMapAsFilesStr, found := podAnnotations[configMapAsFilesKeyName]; found {

...; found && externalConfigMapLoader != nil

pkg/metadata/types/annotations.go, line 213 at r1 (raw file):

			va.FilesForRootfs, err = externalConfigMapLoader(ns, configMapAsFilesStr)
			if err != nil {
				return fmt.Errorf("error loading config map %q as files: %v",

ConfigMap

Reviewable status: 1 change requests, 0 of 2 approvals obtained (waiting on @jellonek and @ivan4th)

docs/README.md, line 16 at r1 (raw file):

Reworded.

pkg/diskimage/diskimage_linux.go, line 96 at r1 (raw file):

Done.

pkg/diskimage/diskimage_linux.go, line 97 at r1 (raw file):

Done.

pkg/diskimage/diskimage_linux.go, line 117 at r1 (raw file):

Done. Also updated in place from which that was copied.

pkg/diskimage/diskimage_linux.go, line 124 at r1 (raw file):

Done. As above.

pkg/diskimage/diskimage_linux.go, line 141 at r1 (raw file):

Done.

pkg/diskimage/diskimage_linux.go, line 150 at r1 (raw file):

Done.

pkg/libvirttools/extdata.go, line 66 at r1 (raw file):

Kinda done ;)

pkg/libvirttools/persistentroot_volumesource.go, line 96 at r1 (raw file):

I'll rething how to do that using virt.StorageVolume interface...
Imo there is no need to double check for FilesForRootfs emptiness as it's the first thing done upon entering to this func, in which case it returns immediately.

pkg/libvirttools/root_volumesource.go, line 106 at r1 (raw file):

Again. Imo there is no need for double check for emptiness (which is also done as a first thing in Put) and error if call occurred. That way it's imo cleaner.

pkg/metadata/types/annotations.go, line 208 at r1 (raw file):

Done.

pkg/metadata/types/annotations.go, line 213 at r1 (raw file):

Reworded.

docs/configmap-as-files.md, line 1 at r1 (raw file):

Reworded.

docs/configmap-as-files.md, line 6 at r1 (raw file):

Done.

docs/configmap-as-files.md, line 10 at r1 (raw file):

Done.

docs/configmap-as-files.md, line 15 at r1 (raw file):

Done.

Reviewed 5 of 11 files at r1, 8 of 8 files at r2.
Reviewable status: 1 change requests, 0 of 2 approvals obtained

Reviewable status: 1 of 2 approvals obtained

Reviewable status: 1 of 2 approvals obtained (waiting on @jellonek)

docs/writing-files-to-rootfs.md, line 3 at r2 (raw file):

# Writing files to root filesystem before VM boot

Virtlet makes it possible to write set of files from to the root filesystem of a VM using

from to?

docs/writing-files-to-rootfs.md, line 21 at r2 (raw file):

where entry is any name, entry_name contains path where file should be

instead of any name I would write any text