First time I was impressed by Linux 9046

The Ghost In The Machine

Most developers with experience writing Servers for Unix or Linux will always configure the system to catch the "HUP" signal and restart the application. This closes all current file-handles and opens a new set of file handles. Another alternative is to let the server die on HUP and have ipconfig start a new deamon when the next incoming message is received. Again, same overall effect.

Xen is an open source Virtual Machine manager, similar to VM-CMS or ZVM on Mainframes, or VMWare on PCs. Xen enabled kernels share a common "master" resource manager - something like a cross between a microkernel and a regular Linux kernel, that can start other "kernels" that can be configured with Linux or Windows.

Xen makes it possible to run different kernels with different environments, for example, if one application - such as a database, needs one version of a library, and another application needs a different version of the same library - and the two would conflict - Xen would let you run both applications on the same box, but on different virtual machines.

Correct - HUP actually goes back to BSD, and probably even to the Open Source versions of AT&T UNIX (Version 6, for example).

Correct. Nearly all databases have something like this - a dbdump type utility. It allows you to dump the contents of the database into a "flat file" - it also lets you mark the transaction logs, so that you can be as up-to-date as possible - but always in sync at the transactional level (no uncommitted partial updates).

Often, however, administrators will opt to take a "snapshot" of the database, which can then be taken completely off-line for the dbdump, which buttures known state for the offline database.