First time I was impressed by Linux 9045

This little feature has many other critical functions.

In the *nix filesystems, the file is defined by an i-node, and the directory entry simply points to an i-node. If you delete a file, but a program still has that i-node open, it won't disrupt that running program.

This also means that you can rename a file, even as it is being written. This makes it MUCH easier to rotate logs - without having to shut down servers. It also makes it possible to upgrade libraries. In fact, on Linux, the only time a system needs to be rebooted is if the actual kernel itself is being replaced or upgraded - for example, switching from a standard kernel to a Xen based kernel.

In addition, Linux has a future called the "Hangup" signal. Historically, it was used to recover a getty when a dialoup modem was disconnected. Most server applications can catch the HUP signal and will reload initialization files - it keeps the down time to almost nothing, often less than a second on modern Linux systems.

This feature also makes it much easier to back-up and restore Linux systems. It's not necessary to switch to a "dumb dos" or other "offline" backup technology. Hot-backups are very common. About the only thing that doesn't back-up well this way is databases - and most databases running on Linux have "hot backup" or "snapshot" facilities to facilitate reliable backups.