Starting and Stopping Apache

Why stop and start your web server? (Answer)

Apache can run several ways:

On Unix, invoked by Inetd
- On-demand, when a request for a web page is received
- Saves memory
- Responds slowly because it must be invoked from scratch for every web page
- Useful only for lightly-used web servers
- Not available on Win32 (Win32 has no inetd)
- To configure, add this line to /etc/services:
  http 80/tcp
  and add this line to /etc/inetd.conf:
  http stream tcp nowait root /usr/sbin/httpd httpd
  (substitute for the pathname as appropriate)
- Make sure you have an inetd running! If you don't, edit the appropriate rc file to get it to start automatically.
- Send it the SIGHUP signal to make it reread its config files.
As a daemon (Unix) or a service (Win32)
- "Standalone" mode
- Runs all the time
- Restarts automatically at boot
- Default
On Win32, in a "console window"
- It runs only when you are logged in...
- And when you explicitly run it.
- For testing and experimentation.

How to Stop and Restart the Server

Unix
- kill -SIGHUP `cat httpd.pid`
- Send the signal to the parent process, not any of its children. If you kill a child, the parent will simply restart it.
Win32 console
- In a DOS window:
  net stop apache net start apache
Win32 service
- Use the Services applet in NT's or Win2K's Control Panel.
- Hint: start menu -> programs -> administrative tools -> services

Lab

See whether Apache is running -- click here:

http://localhost/
If it is, stop it.
Verify that it's not running (click above).
Observe that you get only an error.
Restart it.
Verify that the document is now delivered (click above).
Again, shut it down.
Next, restart it from a console window.
Watch what happens in the Apache Services applet.
Again, verify that it's working (click above).

What Web Servers Do

Now your web server is running... what is it doing, exactly???
It's servicing HTTP requests.
That's why it's called HTTPD (daemon).
But what's HTTP? What's an HTTP request?
The architecture of the HTTP protocol.

Demo

Hand-Simulation of an HTTP Client

Invoke telnet.
Connect to any HTTPD out there on the web via port 80, one of the standard port numbers.
Give it an HTTP request.
See how the server responds.
This technique is useful... why?