Update README.md

README.md

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 # tcpdump as a service
 This is a basic how to for setting up tcpdump to passively monitor network traffic.
-
 In this instance, it is implemented thru a Raspberry Pi using Raspbian Buster Version 10 on a dedicated ethernet interface of eth1.
 
+This service creates pcap files named capture_RRRRRRRR.pcap, where R is a lowercase alphanumeric character, in the /file/location folder.
+Files are 1GB of maximum size and 100 total pcap files are kept.  The oldest will start to be deleted once that number is exceeded.
+
 ## Configure ethernet connection
 ### Determine the ethernet adapter interface that is going to be used
 ```shell