Be default, Eclipse uses a single configuration for a given installation. The
configuration information is saved in the platform.xml file found in the
\configuration\org.eclipse.update dirctory. Them primary content in the
configuration is a list install sites. An install site is a location on the
file
system where an eclipse directory tree. with feature and plugins directories,
can be found.
The configuration identifies what install sites are accessible, lists the
features that
exist in each site, and determines what features are available and active when
Eclipse is started.
The platform:/base/ site is a reference to the eclipse directory structure
from which the eclipse.exe
was started.
解压后的configuration目录 ：
D:\eclipse\eclipse-rcp-indigo-SR1-win32\eclipse\configuration >dir
Volume in drive D is TOOLS
Volume Serial Number is 7899-0DA2
Directory of D:\eclipse\eclipse-rcp-indigo-SR1-win32\eclipse\configuration
2012-10-17 13:45
2012-10-17 13:45
2011-11-02 14:44
2012-10-12 15:35 873 config.ini
2012-10-12 16:52
2011-11-02 14:43
2011-11-02 11:41
2011-11-02 11:41
2012-10-12 16:52
2011-11-02 14:44
2012-10-17 13:45
1 File(s) 873 bytes
10 Dir(s) 5,241,536,512 bytes free
The default configuration is used when Eclipse is launched and applies to
any workspace that might be accessed. The -configuration startup parameter
can
be used to identify an alternnative configuration.
A configuration is a list of install sites and the features found in each of
these install sites.
An install site is a location that contains features and plug-ins that can be
included in the
configuration. The Update Manager processes the content of the features and
plugins directiries of
the install site; if the content is valid, it can be included in
configuration.
platform.xml文件的部分内容 ：
<?xml version="1.0" encoding="UTF-8"?>
<config date="1350027346671" transient="false" version="3.0">
<site enabled="true" policy="USER-EXCLUDE" updateable="true" url="platform:/base/">
<feature id="org.eclipse.wst.xml_ui.feature" plugin-identifier="org.eclipse.wst.xml.ui" url="features/org.eclipse.wst.xml_ui.feature_3.3.1.v201108102009-7H7EFZ3DxumTlaI6nheRdHo2p1KaDIL1Uz-S3PL/" version="3.3.1.v201108102009-7H7EFZ3DxumTlaI6nheRdHo2p1KaDIL1Uz-S3PL">
</feature>
<feature id="org.eclipse.equinox.p2.core.feature" url="features/org.eclipse.equinox.p2.core.feature_1.0.1.R37x_v20110906-8290FZ3FUqIcLqkVkEaTdn_14C7G/" version="1.0.1.R37x_v20110906-8290FZ3FUqIcLqkVkEaTdn_14C7G">
</feature>
</site>
</config>
说白了，configuration的目的就是用来指定Eclipse启动时会加载哪些plugins，会使用哪些branding，会使用哪些参数等。
具体的启动参数可以参见：
from The Java Developer’s Guide to ECLIPSE