adb backup [-f <file>] [-apk|-noapk] [-shared|-noshared] [-all] 
            [-system|-nosystem] [<packages...>]

   - write an archive of the device's data to <file>.

     If no -f option is supplied then the data is written
     to "backup.ab" in the current directory.

       (-apk|-noapk enable/disable backup of the .apks 

         themselves in the archive; the default is noapk.)

       (-shared|-noshared enable/disable backup of the device's

         shared storage / SD card contents; 

         the default is noshared.)

       (-all means to back up all installed applications)

       (-system|-nosystem toggles whether -all automatically 

         includes system applications; 

         the default is to include system apps)

       (<packages...> is the list of applications to be backed 
         up. If the -all or -shared flags are passed, then the
         package list is optional. Applications explicitly 
         given on the command line will be included even if 
         -nosystem would ordinarily cause them to be omitted.)