Debian-Powered Drupal Configuration Policy

Thursday, October 4th, 2012

By Elizabeth Krumbach

LinuxForce’s web hosting services are designed to provide our customers with the benefits of strong security, simple on-going administration and maintenance, and support for the web software to work well in a large number of situations including multi-site support for applications.

We achieve these objectives by operating a Debian infrastructure with close adherence to Debian’s policy, web application policy and PHP policy.

In particular, we use the Debian package for Drupal 6. This provides community supported upgrades with a strong, well-documented policy. Like other software which ships in Debian, the software version is often somewhat older than the most recent upstream release, but it is regularly patched for security by the maintainer and the Debian security team.

In addition, this infrastructure also offers:

  • Only one package needs to be upgraded whenever there is a security patch, instead of every site individually
  • Strong separation from site specific themes, modules, libraries, uploaded files helps keep files you want to edit away from the Drupal core files (which you don’t want to edit)
  • The automation the infrastructure provides disk, memory, and sysadmin time to be minimized, thus reducing costs
  • The benefits of code maturity, as the Debian Drupal maintainers have thought through many boundary cases which it would take our staff time and trial-and-error to re-discover

Site layout

Experienced Drupal admins may find some of the file locations for the package confusing at first, so let’s clarify the differences to ease the transition.

Our infrastructure supports multiple sites per server. This is implemented by providing each site with their own dbconfig.php and settings.php files, plus the following directories:

  • files/
  • themes/
  • modules/
  • libraries/

All of these are configurable by the user, and are located in /etc/drupal/6/sites/drupal.example.com/. The site also inherits the contents of these default directories from core Drupal.

Access to these files via FTP is discussed below.

Core Drupal files are located in /usr/share/drupal6/ and are shared between all the Drupal sites on the server. They should not be edited since all changes to these files will be lost upon upgrade of the Debian Drupal package.

Users & Permissions

A jailed userdrupal FTP account is created to manage the files for the Drupal install.

The userdrupal account is the owner of all the configurable files located in /etc/drupal/6/sites/drupal.example.com/

The system-wide www-data user must have access to the following by having the www-data group own them and be given the appropriate permissions:

  • Read access to dbconfig.php
  • Write access to the files/ directory (this is where Drupal typically stores uploaded files)

All files (with the exception of dbconfig.php) should be writable by userdrupal, the userdrupal group itself is enforced by the system but all users should be configured client-side to respect group read-write permissions to maintain strict security, this is a umask of 002.

Additional Users and non-Drupal Directories

If there is a non-developer who needs to have access to the files directory, for instance, a specific FTP user for that use may be created and added to the userdrupal group.

For ease of administration, if multiple users exist and we are able to support an ssh account (static IP from client required) for handling administration, sudo can be configured to allow said user to execute commands on behalf of the userdrupal ftp user. Remember to add “umask 002” to the .bashrc to respect group read-write permissions.

If additional directories outside the Drupal infrastructure are required for a site, they will be placed in /srv/www/example.com/ and a separate jailed ftp user created to manage the files here. If a cgi-bin is required, it will be placed in /srv/www/example.com/cgi-bin/

Caveats and Cautions

Because of shared use for core Drupal files located in /usr/share/drupal6/ you may experience problems with the following:

  • Some drush commands and plugins assume the drupal files are editable files within the same document root as the rest of your files, thus may not work as expected
  • When you upgrade the drupal6 package all sites are upgraded at once without testing, customers who are concerned about the impact of the upgrade changes and require very high uptimes can be accommodated by testing the site with the upgraded versions of PHP and Drupal in a testing VM
  • Since the Debian package name does not change, you cannot install the drupal6 package from an older Debian version alongside one from a current version, a separate virtualized Debian environment may be needed for testing upgrades if support is uncertain (this issue does not exist with upgrades from drupal6 to drupal7, as they can be installed alongside each other)
  • A policy for handling root level .htaccess files should be developed if they wish to be used

Conclusion

Although the Debian way differs from the Drupal tarball approach, it makes it possible to scale the service to many sites saving disk, memory, and sysadmin effort. By leveraging this Drupal infrastructure provided by Debian, Linuxforce provides one-off Debian package deployments to dedicated systems, shared arrangements for small businesses who are running several sites, and infrastructure deployments for businesses who provide hosting services. We also offer a boutique hosting service for select customers on one of our systems.

Customization, Upgradeability and Eternally Regenerative Software Administration

Friday, October 16th, 2009

By CJ Fearnley

Mary Hayes Weier wrote an interesting article in this week’s edition of InformationWeek on "Alternative IT: CIOs are more receptive than ever to new software models". What is great about her article is how she captured the divergent views on IT models (such as SaaS, cloud computing, etc.) and gave nice vignettes of different organizations trying different parts of various models. I especially valued her use of cognitive dissonance to leave the reader thinking … better informed but without a firm conclusion.

There are so many parts of the article that I could blog about, but the one that touched the core of my thinking about “eternally regenerative software administration” was the quote by Bill Louv, CIO at GlaxoSmithKline, who said

"And here’s the rub: When you customize software, it’s difficult to implement future upgrades from the vendor"

Louv touched the very bane of eternally regenerative software administration! Software should accommodate both customization and upgradeability: these two elements of software administration are at the heart of my notion of eternally regenerative software administration: how to preserve customizations and provide smooth (near zero downtime with almost no glitches) upgrades through major release after major release. It is a big challenge, but in our experience the Free and Open Source Software (FOSS) communities are at the leading edge in finding solutions to these conflicting objectives. Here are some of the innovative ideas from the FOSS world which should serve as models or design patterns for all software developers (if only these ideas would become commonplace!).

First, Debian (a FOSS operating system which is the root of Ubuntu, Knoppix, Xandros and many other Linux distributions) requires that their official packages, a collection of software prepared for easy administration, must adhere to a very mature policy. Debian’s policy is a marvel in the FOSS world and to a very large degree is responsible for its strong support for both customization and upgradeability. I think Debian’s reputation for stability and maintainability is almost certainly due to their decision to develop a consensus-driven policy that its software must implement.

For example, the Debian package maintainer, Luigi Gangitano, for Drupal, a FOSS content management platform, did a great job making the software both customizable and maintainable. The package supports configuration of multiple virtual hosts which can all be upgraded at once! And the Debian drupal6 package stores the look-n-feel in /etc/drupal/6/themes/ so that each site’s GUI can be customized without interfering with upgrades. If only all web applications were built to be as maintainable as Debian’s Drupal package!

Another example is the overlay support included in RT: Request Tracker, a FOSS ticket tracking system. This allows putting replacement subroutines in special files in /usr/local/share/ which overlay or substitute the upstream code. This approach is more likely to break on upgrades, but it supports minimal changes to the business logic with a decent chance that upgrades will be smooth.

There are countless more examples from the FOSS world of innovative solutions to inter-accommodate customization and upgrades in support of eternally regenerative software administration. What are some of your favorite examples?