Neal Walfield: The Hurd is a set of
servers that provide similar interfaces to those found in
traditional Unix-like kernels. The servers, each designed to do one
task or manage one aspect of the system, run in user space thereby
isolating them from both the kernel and each other. This offers
more power and flexibility to both the administrator and the user
and, in doing so, increases system security.
When Unix was created more than thirty years ago, certain
compromises, which given the resources available at the time, made
sense. Time passed and both Unix and computers evolved. However,
the initial compromises, which required rearchitecting central
parts of the system to fix, became design flaws. The Hurd is one
reaction to these defects.
The central concept of the Hurd is that the user is empowered
yet isolated from the system. This does not, and cannot, exist in
Unix: there is just too much core functionality that lives in the
kernel. Why is this bad? Well, it means that parts of the system a
user could take advantage of become off limits.