This is a howto on setting up Django on a Linux (Ubuntu) system using Nginx as a reverse proxy and Gunicorn as a Django service.


Django, Gunicorn, Nginx

The conventional way to run Django in production these days is using Apache2 and mod_wsgi. While there’s nothing wrong with that approach, I prefer Nginx. I also like to be able to control Django server separately from the web server.

There are several production-ready servers for Django. The best seem to be Gunicorn and uWSGI, and Gunicorn seems the best supported and most active project.

When running Django server separately from the web server, we need a way to start, stop and restart the Django server. A popular way for doing it in Django world is Supervisor, altough, for Ubuntu users, Upstart might be less hassle.

You probably already have a Django project you want to deploy, but for completenes’ sake, the steps here will use an empty toy “Hello World” Django project:
Preparation

First things first – you are using virtualenv, right? If not, you should.

virtualenv --no-site-packages test
cd test
source bin/activate
pip install gunicorn django
django-admin.py createproject hello
cd hello
# to test the base setup works
python manage.py runserver 0.0.0.0:8000

Gunicorn

Testing Django with Gunicorn is as simple as:

gunicorn_django -b 0.0.0.0:8000

For production, we might want a bit more options, and we want to make sure the server is executing in the correct environment. The easiest way is to create a shell script to set it all up:

#!/bin/bash
set -e
LOGFILE=/var/log/gunicorn/hello.log
NUM_WORKERS=3
# user/group to run as
USER=your_unix_user
GROUP=your_unix_group
cd /path/to/test/hello
source ../../bin/activate
exec /path/to/test/bin/gunicorn_django -w $NUM_WORKERS \
--user=$USER --group=$GROUP --log-level=debug \
--log-file=$LOGFILE 2>>$LOGFILE

The number of workers is number of worker processes that will serve requests. You can set it as low as 1 if you’re on a small VPS. A popular formula is 1 + 2 * number_of_cpus on the machine (the logic being, half of the processess will be waiting for I/O, such as database). YMMV.

Don’t forget to mark the script as executable (chmod ug+x script.sh). You can run it from the command line for testing. Note that Gunicorn by default uses 127.0.0.1:8000 address (the same as Django debug server), which is fine if Nginx is on the same machine – you usually don’t want to have it wide open to anyone, and instead let Nginx handle incoming connections.

If you want to run several Django servers on the same machine, just make sure each uses a different port number.
Supervisor

Supervisor has extensive documentation, and this blog post is big already, so I’ll just point you to the official docs. The config file for running our server (/etc/supervisor/cont.d/hello.conf on Debian/Ubuntu) should look like this:

[program:hello]
directory = /path/to/test/hello/
user = your_unix_user
command = /path/to/test/hello/script.sh
stdout_logfile = /path/to/logfile.log
stderr_logfile = /path/to/logfile.log

Test it with supervisortcl {start,status,stop} hello (as root).
Upstart

Ubuntu alternative is Upstart, which has a similar config file (/etc/init/hello.conf). An example:

description "Test Django instance"
start on runlevel [2345]
stop on runlevel [06]
respawn
respawn limit 10 5
exec /path/to/test/hello/script.sh

Test it with service hello {start,status,stop} (as root).
Nginx

If you don’t have it set up, you should also install Nginx. The install procedure varies from system to system. On Debian and Ubuntu systems, it’s as simple as apt-get install nginx, and other Linux distributions usually have equivalent commands.

Nginx is mostly a drop-in replacement for Apache for serving static files, though there are some things to set up if you need to run PHP code as well.

For our setup, we need Nginx to serve as the reverse proxy for the upstream server(s). To do so, we add a server section to the config file:

server {
listen 80;
server_name example.com;
# no security problem here, since / is alway passed to upstream
root /path/to/test/hello;
# serve directly - analogous for static/staticfiles
location /media/ {
# if asset versioning is used
if ($query_string) {
expires max;
}
}
location /admin/media/ {
# this changes depending on your python version
root /path/to/test/lib/python2.6/site-packages/django/contrib;
}
location / {
proxy_pass_header Server;
proxy_set_header Host $http_host;
proxy_redirect off;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Scheme $scheme;
proxy_connect_timeout 10;
proxy_read_timeout 10;
proxy_pass http://localhost:8000/;
}
# what to serve if upstream is not available or crashes
error_page 500 502 503 504 /media/50x.html;
}

Ubuntu and Debian systems keep Nginx config files in same layout as for Apache, so the above cold be added to /etc/nginx/sites-available/hello (and enabled by symlinking from sites-enabled directory). Use nginx -t for config test and nginx -s reload to reload the configuration.
That’s it

And that’s it. The services are really quite simple to set up once you know what goes where, the setup is flexible and performant, and the server environments are isolated so it’s possible to host many different services with varying requirements on the same machine.

REFERENCES
http://senko.net/en/django-nginx-gunicorn/

What is phpsuexec?

Phpsuexec is a deprecated feature in cPanel where php is setup as cgi instead of apache module. All shared hosting servers have been updated from phpsuexec to suPHP. This KB applies to such clients that are still using phpsuexec on their VPSs/Dedicated servers. Phpsuexec brings a new level of security to the way php is used.

1) php scripts execute using the permissions of userid of the account holder instead of user “nobody”

2) world writable folders (chmod 777) is not required for file uploads through php

3) The php file need to have ownership of the user to execute in the user account (by default it is).

4) php file (script) does not need 755 permissions. 644 is fine. In fact 400 or 600 is ok too (especially good for sensitive information).

5) php_flag or php_value can NOT be used in .htaccess files (It will result in Internal Server Error).

6) The php flags that do not work in .htaccess can be moved to php.ini file in the same folder where php script exists. However, the php flag/value will be in the format of php.ini and not that of .htaccess. For example this from .htaccess

php_flag register_globals off

will go into php.ini as:

register_globals off

If php.ini exists in the folder where the php scripts exists, it will take all values from it (and nothing will be taken from main php.ini.

7) If the folder that contains a php file/script is world writable (chmod 777), it will result in Internal Server Error. This is similar to cgi/perl scripts under suexec that do not like such permissions for security reason. The normal folder permissions should be 755.

8) Apache specific php functions do not work:

http://www.php.net/manual/en/ref.apache.php

9) If your .htaccess file contains “Options” directive, it should have + or – with the directive to keep the ExecCGI active.

10) Symbolic links do not work for php scripts for security reasons.

11) Some web applications (OS commerce, ZenCart etc.) check if its configure.php file is writable (since php is being executed with userid it should be), so it will complain that its writable. Please change the permissions to 444 via ssh. (chmod 444 /path/to/configure.php)

12) HTTP authentication via php code does not work. However you can continue to use it via .htaccess or password protected folder feature of the control panel.

13) If you use “AddType application/x-httpd-php” in .htaccess, it should be set to “AddHandler application/x-httpd-php”

Similarly if you are using ForceType in .htaccess to force a file to be treated as php, you will need to change it to SetHandler.

What is suPHP?
What is suPHP? What is being changed from phpsuexec to suPHP?

suPHP is a tool for executing PHP scripts with the permissions of their owners. Currently our servers use phpsuexec which also executes PHP with the permission of their owners. However these are two different tools and there are some improvements with moving to suPHP.

Once suPHP is available on your server, you can login to your control panel and find a link ‘PHP Configuration’ under ‘Software/Services’. On that page

1. You can switch your account’s php to php4 or php5

2. You can read how to configure php and how suPHP works. It is similar to phpsuexec as explained above excluding some improvements mentioned below.

3. Download server wide php.ini for php4 or php5 and customize it for your own needs. You may need to do this regularly to keep your php settings in synch with server level settings e.g after Zend Optimizer upgrade.

Changes from phpsuexec to suPHP:

1. By default php CLI is php5. Here are the paths for your reference:

/usr/bin/php (php5 cgi)
/usr/local/bin/php (php5 cli)
/usr/php4/bin/php (php4 cgi)
/usr/local/php4/bin/php (php4 cli)

2. There are some significant improvments in suphp such as

* HTTP based authentication auth works via php
* symbolic links to php files also work
* permissions of public_html does not need to be changed for using shared SSL with php5
* Custom error pages will work with both php4 and php5

3. ionCube PHP Loader will be available server wide alongwith Zend Optimizer. If you use custom php.ini you will need to update it by downloading it from your control panel so that latest Zend Optimizer can load for your scripts as well.

4. If you are setting up custom php settings, the custom php.ini file will be required in a folder where the php script needs to execute. Or you can place php.ini anywhere and have this directive in public_html/.htaccess

suPHP_ConfigPath /home/username/php5-config

where username is your cpanel account username, and php5-config is just a folder name (you can name it anything) and it will pick php.ini from that folder. Yes, you can have php.ini outside of your webroot in suPHP. This is a new feature.

5. To activate php5 on a subfolder or in your whole account, this directive was added in .htaccess in phpsuexec

AddHandler application/x-httpd-php5 .php .php3 .phtml

or a variant of it. Now this must be proceeded by the marker comment to block cpanel from changing your settings:

# Use PHP5 as default
AddHandler application/x-httpd-php5 .php .php3 .phtml

Or if you use control panel to activate php5 (upgraded servers), then you do not need to manually add the above directive.

Other updates

1. For semi-dedicated clients, ffmpeg will be available via both php4 and php5.

2. mod_gzip is being installed as well on all servers.

________________________________________________________

One more time..

Differences between phpsuexec and regular php

When using the common PHP installation on a webserver, php runs as the user nobody and it doesn’t require the execute flag to be enabled.

The problem on this is that if mod_openbasedir is not installed, every user will be able to read your php files because everyone is virtually sharing the same username (nobody).

As most of you already know, PHP Files are not meant to be read, but parsed, and that is where the problem resides. PHP Files have to be parsed, otherwise everyone who is able to read your php file will see settings that you would probably want to keep private, such as your MySQL username and password.

PHPSUEXEC fixes all this because it requires php to be run as the file owner’s username. (for example: andre)

This is not everything it fixes though. PHPSUEXEC is also here to fix file ownership problems. This has been a common issue on a few Content Management Systems such as Joomla and also on the popular blog software: WordPress.

It also adds security to your files as you can use permissions such as 600 or 700 in your files and your visitors will still be able to view them (parsed) in their browsers.

PHPSUEXEC will also refuse to serve any pages that are at security risk, for example with 777 as permissions. (will generate an Internal Server Error)

PHP as an Apache Module

When PHP runs as an Apache module, PHP files work under the Apache user/group known as “nobody”. For example, when a PHP file needs to write to another file or create/remove a file, it does so under the name “nobody”. In order to allow “nobody” to do this, you need to set specific permissions on the file/directory, such as 777 – which translates to read/write/execute by user/group/world. This is insecure because you have not only allowed the webserver (Apache) to read/write to the file, you have also allowed everyone else on the server to read/write to the file as well!

Due to the above conditions, when a PHP file creates or uploads a new file under your account, the new file will be owned by the user “nobody”. If you FTP into your account, all files owned by “nobody” will not be available for you to move, rename or delete. In this case the only way to remove the “nobody” owned files would be through a file on the server or to contact support and ask for the file ownership to be changed back to your username.

PHP as a CGI with Suexec

When PHP runs as a CGI with Suexec, PHP files work under your user/group. PHP files no longer require loose permissions to function, now they will require strict permissions. Setting your directories or PHP files to 777 will cause them to produce a 500 Internal Server Error, this happens to protect your PHP files from being abused by outside sources.

Under PHPSuexec your directories and PHP files can have permissions no greater than 755 (read/write/execute by your username, read/execute by group/world). Since you own your files, your scripts can function in any directory your user has created and can’t be manipulated by any outside users, including “nobody”.

Now, when a PHP file creates or uploads a new file under your account, the new file will be owned by your username. You will no longer have to worry about the webserver taking over your files and even more important, you will no longer have to worry about a stranger reading or writing to your files either!

How To Enable WHM Apache PHP SuExec

By default PHP on WHM/Cpanel is loaded as DSO (Dynamic Shared Object) module and is run by the user “nobody” by default. Though this method of loading the PHP module is normally the fastest way to serve PHP request, running it as using user “nobody” will be a real pain in the ass if you are serving multiple sites run by multiple users, you will be for sure run into file permission problems.

This is where the SuExec comes in play, every executed PHP scripts will be executed by the user who owns the VirtualHost that is server the request, this method has a lot of drawbacks too on both speed and security.

Anyway, if you still want to enable it then read on below.

1. Login to your Web Host Manager as root account then under the Service Configuration menu, look for the “Configure PHP and SuExec” and click on it.

2. On the “Configure PHP and SuExec” page, under “alter configuration” section, look for the PHP handlers and then change its values to “cgi” and then set the Apache SuExec to On. (by default the value is on)

3. Finally, click on “Save new configuration” button and wait til the Apache server restarted and your done.

To verify that SuExec is working as intended, try to upload a file or create a folder using an upload file script on PHP.

That’s all about it.

Troubleshooting Internal Server Errors (Error 500)

Everytime an internal server error occurs, it will be added to your Error Log in cPanel. (cPanel »» Error Log). This will usually give you a clue on where the error resides. In most cases it will be either a permission error on a bad command in your .htaccess file (remember that all php values have to go to your php.ini file).

Directories that need to be written onto will no longer require 777 as permissions and phpsuexec will refuse to write or read on directories exposed with such permissions. You will have to chmod them to 755 always.

To simplify it, just remember that you should never have a file or folder with world-writeable permissions, because you no longer have to.

MIMETypes

If you added a Mimetype to the system in order to run html files as php scripts (AddType as .htaccess command), you will have to remove it and add an ApacheHandler instead. This is easy to do though. Just log into your control panel, then click on Apache Handlers and add the following:

Extension: html (or htm) : AddHandler application/x-httpd-php


REFERENCES
http://www.thinksupport.net/blog/confusion-in-suphp-suphpexec-and-apache-suexec.html

When Apache is compiled as CGI/SuPHP, it allows users to create their own php.ini file under their home directory and modify the php values as per their wish. This may increase security concerns on the server and hence to protect/secure php.ini in SuPHP enabled servers, force every user to use a common php.ini file.

This can be achieved by defining the path of php.ini using suPHP_ConfigPath. To force users to use existing server side php.ini file, create suphp_configpath.conf

# pico /usr/local/apache/conf/userdata/suphp_configpath.conf

and add the following lines

#just specify the path to the php.ini file directory


suPHP_ConfigPath /usr/local/lib/



Once done, save the file and rebuild the Apache configuration so it picks up the changes.

# /usr/local/cpanel/bin/apache_conf_distiller –update –main
# /usr/local/cpanel/bin/build_apache_conf

To verify the include files, execute:

/scripts/verify_vhost_includes

It will display the path to the .conf file you created. Restart the Apache service once

/scripts/restartsrv httpd

This will ensure all the users use the server side php configuration file. If you wish to keep the php.ini elsewhere, just change the value of “suPHP_ConfigPath” and follow the above steps.

REFERENCES
http://linuxhostingsupport.net/blog/tag/what-is-suphp_configpath

REFERNCES
http://www.lowendbox.com/blog/yes-you-can-run-18-static-sites-on-a-64mb-link-1-vps/