persistent device names, anaconda, udev, etc.

[Bill Nottingham <notting redhat com>]

In general, we want the following in the OS:

1) Device names stay consistent across reboots

The current persistent-net.rules udev files, and the current generator
files, handle this.

2) Device names stay consistent across reinstalls

Currently, anaconda doesn't use any existing information when starting
udev (as far as I know), so interfaces can be in random order depending
on timing.

We don't currently have a mechanism for this.

3) Device names stay (reasonably) consistent across hardware swaps or
image distribution to multiple machines (including virt)

i.e., if the image is deployed to a new machine, the devices stay
the same.

We don't currently have a mechanism for this.

So, how to handle this?

For #2, we obviously can't have a set of rule files that does this;
at least not well. (It would need to go back and rename other devices
that we've already gotten events for, for example.) We'd need some sort of
code that runs after udevsettle that applies an ordering.

For #3, the solution proffered is to have the udev writer write two
sets of rules:

- one that maps based on MAC address
- one that maps based on PCI/USB/etc. path

The user could then set a configuration parameter that describes which
ones would actually be used.

Is any of this practical? Is any of this something that we can get done
with existing resources?

Bill