Freezing an Image

You can "freeze" an image to block future changes to it by setting the frozen field to true (example image named xyzImage):

scyld-imgctl -i xyzImage update frozen=true

This blocks updates to any field in the image, stops any field data from being erased, and prevents the image from being deleted.

To re-enable changes, set frozen back to false (the default):

scyld-imgctl -i xyzImage update frozen=false

Anyone who can set frozen=true can also set it to false and thus this mechanism primarily protects against accidental changes to "known good" images. It does not provide significant protection against malicious attacks.