Each one of us has a web server with a welcome page and a simple, working, CGI script written in Perl. We have installed the web server, made the necessary changes to the configuration files and started the web server. Today we want to revisit installation and configuration of Apache because we want to change a few parameters, we want to look at one parameter that we forgot to configure last time, and we want to specify a few more configuration parameters. In the process we clean up our disk space and keep only the relevant files and directories. We review the issues related to starting and stopping the server and introduce a way to start the server automatically (if necessary) to protect it from system reboots.

Once we have a web server that is rock-solid we are ready to move ahead. The plan for this week is to address issues related to:

1. Announcements

You are encouraged to work on assignments together, you'll get to know each other so that you can form project teams.

Also make sure you knof of and make good use of the newsgroup: ac.csci.a348

2. Installation of Apache

Apache should be installed in your directory and the relevant directory structure should be like this:

/u/username/httpd/                    # directory 
/u/username/httpd/httpd               # file 
                 /conf/               # directory
                 /conf/httpd.conf     # file 
                      /srm.conf       # file 
                      /access_conf    # file 
                 /htdocs/             # directory
                 /htdocs/index.html   # file 
                 /cgi-bin/            # directory 
                 /logs/               # directory
                 /logs/access_log     # file 
                 /logs/error_log      # file 
                 /logs/httpd.pid      # file 
Apache descends from NCSA and CERN so the structure is similar.

Here's a quick description of these files and directories.

/u/username/httpd/

This is the ServerRoot directory.
/u/username/httpd/httpd
This file is the actual web server. You need to restart your server every time you make a change to one of your configuration files.
/u/username/httpd/conf/
This directory contains configuration files.
/u/username/httpd/conf/httpd.conf
This is the server's main configuration file.
/u/username/httpd/conf/srm.conf
This is the server resource configuration file.
/u/username/httpd/conf/access_conf
This is the global access control file.
/u/username/httpd/htdocs/
This is the DocumentRoot directory.
/u/username/httpd/htdocs/index.html
This is the server's welcome page.
/u/username/httpd/cgi-bin/
This is the CGI scripts directory.
/u/username/httpd/logs/
This directory contains log files.
/u/username/httpd/logs/access_log
The accesses to your site are logged here.
/u/username/httpd/logs/error_log
The server logs here any errors that hit has to report.
/u/username/httpd/logs/httpd.pid
This file contains the process id of the server.
3. Configuration of Apache


httpd.conf

In what follows please use your username instead of dgerman, your host name for tucotuco, and your port number for 19800. The file below is the one for the following assignment:

Your assignments should be different so please be aware of that.
tucotuco.cs.indiana.edu% diff httpd.conf httpd.conf-dist
32c32
< Port 19800
---
> Port 80
52c52
< User dgerman
---
> User nobody
58c58
< ServerAdmin dgerman@indiana.edu
---
> ServerAdmin you@your.address
66c66
< ServerRoot /u/dgerman/httpd  
---
> ServerRoot @@ServerRoot@@
127c127
< LockFile /tmp/apache.lockfile.dgerman
---
> #LockFile logs/accept.lock
185,186c185,186
< MinSpareServers 1  
< MaxSpareServers 3 
---
> MinSpareServers 5
> MaxSpareServers 10
190c190
< StartServers 1 
---
> StartServers 5
tucotuco.cs.indiana.edu% 

So we change:


srm.conf

Please use your username instead of dgerman.

tucotuco.cs.indiana.edu% diff srm.conf srm.conf-dist  
15c15
< DocumentRoot /u/dgerman/httpd/htdocs
---
> DocumentRoot @@ServerRoot@@/htdocs
20c20
< UserDir httpd/htdocs  
---
> UserDir public_html
143c143
< Alias /icons/ /u/dgerman/httpd/icons/
---
> Alias /icons/ @@ServerRoot@@/icons/
148c148
< ScriptAlias /cgi-bin/ /u/dgerman/httpd/cgi-bin/
---
> #ScriptAlias /cgi-bin/ @@ServerRoot@@/cgi-bin/
tucotuco.cs.indiana.edu% 
So we change:


access.conf

Please use your username instead of dgerman.

tucotuco.cs.indiana.edu% diff access.conf access.conf-dist
28c28
< <Directory /u/dgerman/httpd/htdocs>
---
> <Directory @@ServerRoot@@/htdocs>
54c54
< <Directory /u/dgerman/httpd/cgi-bin>
---
> <Directory @@ServerRoot@@/cgi-bin>
tucotuco.cs.indiana.edu%
So we change two pathnames for:
4. Starting the server

If your server is not running already you need to login into your host and type the following command:

/u/username/httpd/httpd -d /u/username/httpd
where username is your username.

If your server is already running and if you're working on the host that you should be working on you won't be able to start the server with the command above. See restarting the server below.

To check if your server is running or not use:

/usr/bin/ps -ef | grep httpd | grep username
where username is your username. This should also return the server's pid.

5. Stopping the server

This can be done with:

kill -TERM `cat /u/username/httpd/logs/httpd.pid`
Make sure you notice the backquotes (`) above.

If the file does not exist you shoudl find the pid of the server (as described before) and use

kill -TERM pid
where pid is the process id, that is, a(n up to 5-digit) number.

6. Restarting the server

kill -HUP `cat /u/username/httpd/logs/httpd.pid`
Same considerations apply.

8. Log files

Significant events, such as starting, stopping, restarting, and errors in general are recorded in error.log. This file is useful for debugging CGI scripts and monitoring the server in general.

access.log contains a log of all calls to your server.

7. Protecting the server from machine reboots

Use starthttpd (written by Steve Kinzler) to start and stop the server.

Copy it into your bin directory:

cp /u/dgerman/bin/starthttpd /u/username/bin/starthttpd-template
cp /u/username/bin/starthttpd-template /u/username/bin/starthttpd
(Replace username with your username but do copy it from my account).

Then use the editor of your choice to change the script for your account such that the differences are like this:

tucotuco.cs.indiana.edu% diff starthttpd starthttpd-template
6c6
< HTTPD_HOST=tucotuco.cs.indiana.edu            # Server host
---
> HTTPD_HOST=yourhost.cs.indiana.edu            # Server host
11c11
< basecmd="/u/dgerman/httpd/httpd -d $httpd"
---
> basecmd="/u/username/httpd/httpd -d $httpd"
tucotuco.cs.indiana.edu% 
Use crontab to schedule starthttpd.
tucotuco.cs.indiana.edu% crontab -e
tucotuco.cs.indiana.edu% crontab -l
0 6 * * * /u/dgerman/bin/starthttpd 
tucotuco.cs.indiana.edu%
This starts the server (if necessary) every day at 6am.

8. Javascript calculator

Here's the example discussed in class:

<html>
<head>
<title>
A Javascript Calculator
</title>
<script language="Javascript">
function computeAdd (obj) {
  obj.res.value = eval (obj.val1.value) + 
                  eval (obj.val2.value); 
}
function computeSub (obj) {
  obj.res.value = eval (obj.val1.value) -
                  eval (obj.val2.value); 
}
</script>
</head>
<body>
<form>
Operator 1: <input type="text" name="val1" value="0"> <br>
Operator 2: <input type="text" name="val2" value="0"> <br>
<input type="button" value="Add" onclick="computeAdd(this.form)"> <p> 
<input type="button" value="Sub" onclick="computeSub(this.form)">
Result: <input type="text" name="res"> <hr> 
<hr> 
</form>
</body>
</html>
and here it is in action:


Op 1:
Op 2:
Result:

... to be continued