What are the main reasons against the Windows Registry?

If i want to develop a registry-like System for Linux, which Windows Registry design failures should i avoid?
Which features would be absolutely necessary?
What are the main concerns (security, ease-of-configuration, ...)?

I think the Windows Registry was not a bad idea, just the implementation didn't fullfill the promises. A common place for configurations including for example apache config, database config or mail server config wouldn't be a bad idea and might improve maintainability, especially if it has options for (protected) remote access.

I once worked on a kernel based solution but stopped because others said that registries are useless (because the windows registry is)... what do you think?

Solution

I once worked on a kernel based solution but stopped because others said that registries are useless (because the windows registry is)... what do you think?

A kernel-based registry? Why? Why? A thousand times, why? Might as well ask for a kernel-based musical postcard or inetd for all the point it is putting it in there. If it doesn't need to be in the kernel, it shouldn't be in. There are many other ways to implement a privileged process that don't require deep hackery like that...

If i want to develop a registry-like System for Linux, which Windows Registry design failures should i avoid?

Make sure that applications can change many entries at once in an atomic fashion.
Make sure that there are simple command-line tools to manipulate it.
Make sure that no critical part of the system needs it, so that it's always possible to boot to a point where you can fix things.
Make sure that backup programs back it up correctly!
Don't let chunks of executable data be stored in your registry.