Dependencies

[Aidan Thornton]

> I've played with initng as well; I liked it a lot, but it is very easy to
> wedge initng, and this happens a lot on seemingly trivial upgrades.  So now
> I'm back to using Gentoo's vanilla init.

Ah yes. The code related to upgrading is one of the more fragile parts
of InitNG. (As I'm sure most of you know, if init or any of its
libraries is upgraded, init needs to be restarted or remounting the
root filesystem read-only will fail on the next shutdown).

I presume Upstart won't fall into this trap and will have a reliable,
backwards-compatible way of reloading itself and restoring its state.

> Great.  I'm very interested in following this discussion.  As I mentioned, I
> was trying to build a set of Upstart event handlers for Gentoo, which already
> has a sophisticated -- but not event driven -- init system, supporting
> complex and conditional dependencies.  The conversion raises a lot of
> questions about how the same jobs will be done under Upstart, but I'd love to
> at least get to a point where I can boot the system under the new init
> process :-)

I don't think Gentoo's init system is particularly complex, it's just
not currently compatible with Upstart - all dependency-based init
systems will probably have the same problem. ("Use" conditional
dependencies could probably best be approximated by waiting for the
service if it exists and isn't disabled, but this wouldn't always help
as, in an event-driven system, I don't think it's ever possible to be
sure if the dependent service will be started.)

By the way, I assume that there'll eventually be some way of varying
the set of events required to start a service depending on a config
file? For example, I want MythTV to start even if no network interface
is up (since I need to record stuff even when I have no network
connection), but people with slave backends (or a seperate MySQL
server machine) probably want them to start after the network
interface is up...