[atomic-devel] Centralized Overrides?

[Jeremy Eder <jeder redhat com>]

Hi,

Since RHEL Atomic descends from RHEL (and same with CentOS/Fedora), we inherit some defaults in a growing list of areas that don't make sense for a specialized container distribution.  We resolved many of the performance issues in the last year or so, using the tuned profile delivery vehicle.  But there are others appearing now that might not fit in tuned, whether it's for technical (build tooling) or political reasons.  At least:

- specialized selinux booleans (for use by NFS clients).
- specialized handling of LVM auto-extend (for use by docker-storage-setup).

Instead, I think we should come up with a delivery vehicle for centralized overrides.  This would provide analogous functionality to tuned (where we centralize tunings).  This is similar in concept to "alternatives".

Tuned provides "profiles" for optimizing different workloads.  Over time, I could see this centralized overrides approach growing in scope across products.  It's also quite possible that tuned could be extended through plugins to fill this need.

Override functionality could also play a role when a layered product (RHEV) needs to, but doesn't want to, have to add packages to the Atomic base package list.  IOW alternatives specifies a layered product's own container, and that gets pulled into the system by this new overrides method either at build- or run-time.

The end goal here might be a single, very small Atomic distro, and a family of override profiles that are the consolidated place for customizing variants of our products.

Are there plans for this already?  Does anyone know of an existing mechanism that offers this feature?