Apache Felix User Admin File-based store
Copyright 2012 The Apache Software Foundation

This bundle provides a file-based store for use with the Felix UserAdmin
service. It uses a binary file-format to persist the role information. This
file will always be written in the data area of the bundle and be called
"ua_repo.dat".

The file-based store service this bundle provides can be configured at 
runtime by using the service PID "org.apache.felix.useradmin.filestore". The 
configuration options recognized by this service are:

"background.write.disabled"
   by default, all changes made to the UserAdmin repository are flushed to
   disk. By setting this value to "false", this no longer will happen for each
   change, but only upon stopping of the service. This value is optional and 
   defaults to "false";
"background.write.delay.value"
   denotes the period after which the changes should be persisted to disk. If
   other changes to the repository occur during this period, the period will
   start over. This value is optional and defaults to "500";
"background.write.delay.timeunit"
   denotes the time unit for "background.write.delay.value". This value is
   optional and defaults to "milliseconds". Possible values are: "days", 
   "hours", "minutes", "seconds", "milliseconds", "microseconds" and 
   "nanoseconds".

Alternatively, one can also supply the above mentioned configuration keys 
prefixed with "org.apache.felix.useradmin.filestore." as system properties. 
For example by adding the following to your JVM arguments:

  -Dorg.apache.felix.useradmin.filestore.background.write.disabled=true
  
will disable persisting the changes on each change of the UserAdmin roles.

However, using system properties will imply that only a single store can be 
configured on a system (which could be a sensible default for some 
situations)!