Newbie Question About System Update

[Kövesdán Gábor]

> This is generally not the case.  Unix lets you continue to access a 
> file after it has been deleted, so long as the process hangs on to a 
> file descriptor. This lets you replace programs in use, without 
> running into the same problems that platforms like Windows have.

Though this is true, I discourage You to upgrade a running system. I 
tried to upgarde 5.3-RELEASE to 5-STABLE without booting to single user 
mode. I simply sent a TERM signal to most of the processes, and tried to 
make installworld. There was some error messages, the system crashed and 
didn't boot anymore...