Python CGI on Amazon AWS EC2 micro-instance -- a how-to!
- by user595585
How can you make an EC2 micro instance serve CGI scripts from lighthttpd? For instance Python CGI?
Well, it took half a day, but I have gotten Python cgi running on a free Amazon AWS EC2 micro-instance, using the lighttpd server. I think it will help my fellow noobs to put all the steps in one place. Armed with the simple steps below, it will take you only 15 minutes to set things up!
My question for the more experienced users reading this is: Are there any security flaws in what I've done? (See file and directory permissions.)
Step 1: Start your EC2 instance and ssh into it.
[Obviously, you'll need to sign up for Amazon EC2 and save your key pairs to a *.pem file. I won't go over this, as Amazon tells you how to do it.]
Sign into your AWS account and start your EC2 instance. The web has tutorials on doing this. Notice that default instance-size that Amazon presents to you is "small." This is not "micro" and so it will cost you money. Be sure to manually choose "micro." (Micro instances are free only for the first year...)
Find the public DNS code for your running instance. To do this, click on the instance in the top pane of the dashboard and you'll eventually see the "Public DNS" field populated in the bottom pane. (You may need to fiddle a bit.) The Public DNS looks something like:
ec2-174-129-110-23.compute-1.amazonaws.com
Start your Unix console program. (On Max OS X, it's called Terminal, and lives in the Applications - Utilities folder.)
cd to the directory on your desktop system that has your *.pem file containing your AWS keypairs.
ssh to your EC2 instance using a command like:
ssh -i <<your *.pem filename>> ec2-user@<< Public DNS address >>
So, for me, this was:
ssh -i amzn_ec2_keypair.pem [email protected]
Your EC2 instance should let you in.
Step 2: Download lighttpd to your EC2 instance.
To install lighttpd, you will need root access on your EC2 instance. The problem is: Amazon will not let you sign in as root. (Not straightforwardly, at least.) But there is a workaround. Type this command:
sudo /bin/bash
The system prompt-character will change from $ to #. We won't exit from "sudo" until the very last step in this whole process.
Install the lighttpd application (version 1.4.28-1.3.amzn1 for me):
yum install lighttpd
Install the FastCGI libraries for lighttpd (not needed, but why not?):
yum install lighttpd-fastcgi
Test that your server is working:
/etc/init.d/lighttpd start
Step 3: Let the outside world see your server.
If you now tried to hit your server from the browser on your desktop, it would fail. The reason: By default, Amazon AWS does not open any ports to your EC2 instance. So, you have to open the ports manually.
Go to your EC2 dashboard in your desktop's browser. Click on "Security Groups" in the left pane. One or more security groups will appear in the upper right pane. Choose the one that was assigned to your EC2 instance when you launched your instance.
A table called "Allowed Connections" will appear in the lower right pane. A pop-up menu will let you choose "HTTP" as the connection method.
The other values in that line of the table should be: tcp, 80, 80, 0.0.0.0/0
Now hit your EC2 instance's server from the desktop in your browser. Use the Public DNS address that you used earlier to SSH in. You should see the lighttpd generic web page. If you don't, I can't help you because I am such a noob. :-(
Step 4: Configure lighttpd to serve CGI.
Back in the console program, cd to the configuration directory for lighttpd:
cd /etc/lighttpd
To enable CGI, you want to uncomment one line in the < modules.conf file. (I could have enabled Fast CGI, but baby steps are best!) You can do this with the "ed" editor as follows:
ed modules.conf
/include "conf.d\/cgi.conf"/
s/#//
w
q
Create the directory where CGI programs will live. (The /etc/lighttpd/lighttpd.conf file determines where this will be.) We'll create our directory in the default location, so we don't have to do any editing of configuration files:
cd /var/www/lighttpd
mkdir cgi-bin
chmod 755 cgi-bin
Almost there! Of course you need to put a test CGI program into the cgi-bin directory. Here is one:
cd cgi-bin
ed
a
#!/usr/bin/python
print "Content-type: text/html\n\n"
print "<html><body>Hello, pyworld.</body></html>"
.
w hellopyworld.py
q
chmod 655 hellopyworld.py
Restart your lighttpd server:
/etc/init.d/lighttpd restart
Test your CGI program. In your desktop's browser, hit this URL, substituting your EC2 instance's public DNS address:
http://<<Public DNS>>/cgi-bin/hellopyworld.py
For me, this was:
http://ec2-174-129-110-23.compute-1.amazonaws.com/cgi-bin/hellopyworld.py
Step 5: That's it! Clean up, and give thanks!
To exit from the "sudo /bin/bash" command given earlier, type:
exit
Acknowledgements: Heaps of thanks to:
wiki.vpslink.com/Install_and_Configure_lighttpd
www.cyberciti.biz/tips/lighttpd-howto-setup-cgi-bin-access-for-perl-programs.html
aws.typepad.com/aws/2010/06/building-three-tier-architectures-with-security-groups.html
Good luck, amigos! I apologize for the non-traditional nature of this "question" but I have gotten so much help from Stackoverflow that I was eager to give something back.
