Dump module should support an option to roll the files

[trunkfullofgoats]

In Linux systems "logrotate" is commonly used to perform this action, however, the program (daq_dump) would have to interpret something along with that (a signal perhaps?) to indicate that the file should be opened by name (thus getting a descriptor to the new empty log file.

Alternatively, this could be supported internally by the module as well by enabling it with a daq var by specifying a roll size / count of packets / time or whatever. IMO rolling by packet count or size would be ideal.