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GLEP: 11
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Title: Web Application Installation
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Version: $Revision: 1.5 $
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Last-Modified: $Date: 2004/01/31 21:56:55 $
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Author: Troy Dack <tad@gentoo.org>
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Author: Stuart Herbert <stuart@gentoo.org>
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Discussions-To: gentoo-dev@gentoo.org
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Status: Final
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Type: Standards Track
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Content-Type: text/x-rst
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Created: 02-August-2003
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Post-History: 07-Aug-2003, 12-Aug-2003, 13-Aug-2003, 3-Sep-2006
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Status
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======
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As of 2006-09-03 the webapp eclass has existed for some time.
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Credits
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=======
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Based on comments posted to gentoo-dev mailing list [#WebAppPost1]_
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[#WebAppPost2]_ [#WebAppPost3]_ by:
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Stuart Herbert <stuart at gentoo.org>, Max Kalika <max at gentoo.org>,
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Robin H.Johnson <robbat2 at gentoo.org> and others
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Definitions
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===========
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*Web Application*
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an application that requires a web server to function and interacts with
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the user via a browser
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*Web Application Instance*
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An apparent install of the Web Application that is served up via the
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webserver. There may be any number of instances per Web Application.
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This is a major use for web applications. Our Gentoo Zope setup
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already provides instances and can be used for some concepts on this
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matter.
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*Web Application Setup Program*
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A script similar in function to zope-config that sets up instances.
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*Document Root*
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a location in the file system that forms the main document tree visible from
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the web
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Conventions
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===========
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When describing the location of a directory in the file system it
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wil be shown *with* a trailing slash, eg::
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/foo/bar/
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When describing the location of a specific file (irrespective of any
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file extention) it will shown *with out* a trailing slash, eg::
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/foo/blah
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Abstract
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========
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To define where and how web based applications should be installed by Gentoo.
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Motivation
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==========
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Currently there is no standard defined regarding the installation of web
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based applicaitons in Gentoo. This leads to ebuild authors creating a
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variety of methods to determine:
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* where the application should be installed
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* what user and permissions the application should be given
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* where any configuration files related to the application should be
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installed.
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Due to a lack of standard install method configuration files are at
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risk of being overwritten during upgrade, potentially causing system
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administrators down tine as they have to reconfigure web applications
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after an upgrade.
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Rationale
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=========
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A discussion on the gentoo-dev mailing list [#WebAppPost1]_ raised the
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following points regarding how Gentoo handles the installation of web based
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applications:
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1. Gentoo installed web applications (eg: horde, phpbb, cacti,
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phpmysql) should not be installed in the Document Root of a web server.
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2. Web applications should not have their configuration files installed
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under the Document Root of a web server.
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i. Web Application must be slotted by their full version numbers to
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further avoid downtime when true configuration changes are required.
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3. Web applications should not be owned by the same user as the web server.
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4. It should be easily possible to have multiple instances of a web
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application without any duplication of source files.
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5. It should be immediately apparent how to control instances of a web
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application.
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Implementation
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==============
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Max Kalika <max at gentoo.org> stated that he has a preliminary eclass that
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implements a good deal of this GLEP.
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Stuart Herbert <stuart at gentoo.org> has committed::
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webapp-apache.eclass
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to CVS, this is a stop-gap measure whilst this GLEP is being finalised.
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1. Web Server
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-------------
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A common default web server should be selected. Selection of a default web
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server will help to reduce the number of bugs that are reported.
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Given the popularity of the Apache web server it is suggested that Apache be
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selected as the Gentoo default web server.
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The Virtual Host Configuration tool (see below) will transparently support
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different web servers, thus enabling web applications to be installed on a
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Gentoo system irrespective of the installed web server.
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1.1 Default Document Root
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'''''''''''''''''''''''''
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The current default Document Root for Gentoo is /home/httpd/, this is
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unsuitable for a couple of reasons:
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* /home/ may be exported via nfs to numerous other hosts, it is not
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acceptable to share publically accessible files with numerous hosts.
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* there is a potential (all be it small) for a user name clash
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To ensure the greatest flexibility when installing applications the following
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*Document Root* locations are to be used:
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* For single host installations::
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/var/www/localhost/
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* For multiple virtual host installations::
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/var/www/<fully qualified domain name>/
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eg:
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/var/www/www.gentoo.org/
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Additionally the chosen location ( /var/www/ ) appears to be becoming a defacto
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standard for Linux distributions.
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1.2 Apache 2
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''''''''''''
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All web application .ebuilds will honour any USE flags that are intended to
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add support for Apache 2 as well as supporting Apache 1 installations.
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2. Application Installation
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---------------------------
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The current accepted standard Document Root in Gentoo is /home/httpd. The
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discussion suggest that this is not the best location to install web based
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applications.
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2.1 Application SLOTs
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'''''''''''''''''''''
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All ebuilds are to set the SLOT variable as follows::
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SLOT="${PV}"
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Setting the SLOT variable as shown will enable different versions of the same
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web application to be served concurrently by one server.
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2.2 Installation Paths
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''''''''''''''''''''''
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Web applications should be installed outside of the Document Root using the following
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defaults:
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* for files to be served to clients::
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/usr/share/webapps/${PF}/htdocs/
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/usr/share/webapps/${PF}/cgi-bin/
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* install *site default* configuration files in::
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/etc/webapps/${PF}/
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* for documentation files (not served to clients)::
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/usr/share/doc/${PF}/
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3. Virtual Host Support
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-----------------------
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The ability to easily configure and administer multiple virtual hosts is a
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must.
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3.1 New "vhost" USE Flag
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''''''''''''''''''''''''
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To enable support for multiple virtual host installations a new USE flag is
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to be added to Portage. The use flag will be::
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vhost
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When *vhost* is _set_ the installation location and configuration for the web
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application will be effected, see below for more details.
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3.2 VHost Configuration Tool
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''''''''''''''''''''''''''''
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To assist administration of multiple virtual hosts a "VHost Configuration Tool"
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needs to be developed and implemented. Initial discussion regarding the VHost
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Config tool and proposed usage can be found at http://article.gmane.org/gmane.linux.gentoo.devel/10874.
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It's the job of the VHost Config toolset to make a local instance of the web
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application run under a specific web server.
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The VHost Configuration Utility will need to be a seperate package, maintained by Gentoo.
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Web Server .ebuilds will require the VHost Config tool as a dependency (DEPEND).
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`Bug #26293`_ will be used to track the initial progress of the VHost
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Configuration Tool.
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.. _Bug #26293: http://bugs.gentoo.org/show_bug.cgi?id=26293
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The vhost-config must do three main things:
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- creates directories (copies a skeleton directory for the most part).
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- create web server vhost config files.
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- HUP web server so it reads in the new config without stopping.
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Initially the VHost Config tool should provide support for the Apache web
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server. As the tool matures support for other web servers can be added.
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3.3 Single Host Installation
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''''''''''''''''''''''''''''
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For single host installations the .ebuild will make the required
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configurations changes and symlinks using the VHost Config tool to ensure
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that the web application is available to be served from::
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/var/www/localhost/htdocs/${PF}/
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In this case it may be feasible for the VHost Config tool to simply symlink the
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directories from /usr/share/webapps/${PF}/ as is appropriate.
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3.4 Virtual Host Installation
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'''''''''''''''''''''''''''''
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For installations that support multiple virtual hosts the .ebuild will
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install the web application into the default location and then leave configuration
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to the user through the VHost Config tool.
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In this case the web application files will be copied from
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/usr/share/webapps/${PF}/ to /var/www/<FQDN>/ by the VHost Config tool.
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3.5 Configuration Files
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'''''''''''''''''''''''
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As stated above web application *site default* configuration files are to be
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installed into::
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/etc/webapps/${PF}/
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The files in this directory are then copied (not symlinked!) by the VHost
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Config tool to the Document Root for each instance of the app that is installed.
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This will require the VHost Config toolset to emulate Portage's CONFIG_PROTECT
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behaviour for the web applications.
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4. Application Permissions
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--------------------------
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Installing web applications and giving the web server ownership of the files
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is a security risk. This can possibly lead to application configuration
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files being accessed by unwanted third parties.
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All web applications should be owned by *root* unless the application
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absolutely requires write access to its installation directories at execution
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time.
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Backwards Compatibility
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=======================
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There may be some issues regarding compatibility with existing installs of
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web applications. This is particularly true if the default Document Root is
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moved from what is accepted as the current standard (/home/httpd).
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The main issues are:
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* transition of existing configuration files to the
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/etc/webapps/${PF}/ directory.
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* modification/reconfiguration of applications so that they
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are aware of the location of configuration files.
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* creating the VHost Config toolset to enable installation and
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configuration of web applications irrespective of web server.
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References
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==========
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.. [#WebAppPost1] http://article.gmane.org/gmane.linux.gentoo.devel/10411
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.. [#WebAppPost2] http://news.gmane.org/onethread.php?group=gmane.linux.gentoo.devel&root=%3C1059843010.5023.80.camel%40carbon.internal.lan%3E
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.. [#WebAppPost3] http://news.gmane.org/onethread.php?group=gmane.linux.gentoo.devel&root=%3C86960000.1060038977%40valkyrie.lsit.ucsb.edu%3E
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Copyright
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=========
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This document has been placed in the public domain.
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