Where to store application data (non-user specific) on Linux

In my OSGi-based Java app I am developing a bundle to provide the rest of the system with access to the file system. In addition to providing access to the user home directory, I also wish to provide access to a non-user specific area. Exactly what this area will be used for is as yet undetermined, but it will not be for preferences (handled by a different bundle), however it may be used to store data that could change at runtime.

I intend on using the following directories for this purpose:

• Windows Vista & Windows 7: “\ProgramData”.
• Windows XP: “\Documents and Settings\All Users“.
• Mac OS X: “/Library/Application Support”.

Where is a sensible equivalent in Linux and how do I get a handle on it from my Java code?

It depends on what kind of data you're planning on storing. This answer is under the premise that you're storing and modifying data at runtime.

Contrary to what others have suggested, I would recommend against using /usr/share for storage. From the Filesystem Hierarchy Standard:

The /usr/share hierarchy is for all read-only architecture independent data files.

As you're modifying data, this goes against the read-only nature of the /usr subsystem.

A seemingly better place to store your application state data would be /var, or more specifically, /var/lib. This also comes from the Hierarchy Standard. You could create a /var/lib/myapp, or if you're also using things like lock files or logs, you could leverage /var/lock or /var/log.

Have a deeper look at the standard as a whole (linked to above) - you might find a place that fits what you want to do even better.

Like Steve K, I would also recommend using the Preferences API for application preference data.

It depends.

• Global configuration -> /etc/appname

• Read-only, independent of machine architecture -> /usr/share/appname

• Read-only, machine specific -> /usr/lib/appname

• Read-write -> /var/lib/appname

No guarantee for completeness, please check the Filesystem Hierarchy Standard.

Since you are using Java, have you looked at the Preferences API?

From the introduction:

Applications require preference and configuration data to adapt to the needs of different users and environments. The java.util.prefs package provides a way for applications to store and retrieve user and system preference and configuration data. The data is stored persistently in an implementation-dependent backing store. There are two separate trees of preference nodes, one for user preferences and one for system preferences

I'd let the built in API do the work.

The freedesktop.org (previously known as the X Desktop Group) project has defined some standards for this in the XDG Base Directory Specification.

In your case, I'd have a look at $XDG_DATA_DIRS:

$XDG_DATA_DIRS defines the preference-ordered set of base directories to search for data files in addition to the $XDG_DATA_HOME base directory. The directories in $XDG_DATA_DIRS should be seperated with a colon ':'.

If $XDG_DATA_DIRS is either not set or empty, a value equal to /usr/local/share/:/usr/share/ should be used.

I warmly suggest to read the XDG Base Directory Specification.

In /usr/share or /usr/local/share folders