The mongo shell should provide a way for executing system commands from inside the shell. This would make the http://www.mongodb.org/display/DOCS/fsync+Command#fsyncCommand-Lock%2CSnapshotandUnlock procedure easier and more self-contained.

essentially:

db.runCommand(

)

system("/path/to/my-filesystem-snapshotting-script.sh")

db.$cmd.sys.unlock.findOne();