Q: What is graceful Apache restart
A: Advise children to exit after current requests, as child dies off the parent replaces it with a new generation of child.
Command to use: apachectl –k graceful

Q: Know anything about Apache configuration file directive
A: for communication between server and child processes. If directive not specificed create ScoreBoard entirely in memory (Anonymous Standard Memory), otherwise, file-based share-memory(on-disk), to gain performance: use RAM disk…

Q: TCP socket programming, what is SO_REUSEADDR
A: Server restart control mechanism, reuse that old binded address please. This is especially popular in Apache source.