Filesystem layout and concepts

imgbased makes a few assumptions about file locations and how the filesystem is organized in order to make upgrades work correctly These concepts have been clearly defined by OSTree, and the Stateless project from systemd.

Overview

A few relevant points are:

• Only /etc and /var are writable and persisted.
• Vendor presets/configuration goes to /usr/etc
• User configuration goes to /etc
• User configuration overrides the vendor presets
• Partial configuration snippets can be placed in .d

The assumption is that these mechanisms provide enough structure to build robust upgrades.

NOTE: Following these guidelines is one critical point to allow stable upgrade and rollback.

Open Items

FIXME

• Identify packages which modify config outside of /etc - use imgbase diff
• Patches for other packages to support the above schema, like https://gerrit.ovirt.org/#/c/48317/
• Node identifier /etc/os.release.d/50-ovirt-node with VARIANT field