Each subcommand has a dedicated set of flags for configuration.
List the flag names, a short description and their default values with:
$ net <subcommand> -h
All default values for flags can be overriden via environment variables, by using the flag name and prefixing it with "NC_", for example lets overwrite the -read flag from net capture:
$ NC_READ=/home/user/traffic.pcap net capture
Since the provide the value via the environment, passing it via flag is no longer necessary. This is generally useful to enable or disable features globally on your system.
Additionally, the configuration can be provided as a config file via the -config flag.
To retrieve a sane default configuration for the subcommand you want to execute, use the -gen-config flag and redirect the output into a file:
$ net capture -gen-config > capture.conf
The config file will look something like this, using the name value syntax to set values:
...# toggle promiscous mode for live capturepromisc true# don't print infos to stdoutquiet false# reassemble TCP connectionsreassemble-connections true# resolve ips to domains via the operating systems default dns resolverreverse-dns false# use serviceDB for device profilingserviceDB false# configure snaplen for live capture from interfacesnaplen 1514# print netcap package version and exitversion false# wait for all connections to finish processing before cleanupwait-conns true# number of workersworkers 12# write incomplete responsewriteincomplete false...
Lines starting with # are treated as comments, blank lines are being ignored.
Adjust the parameters of interest and pass the config file:
$ net capture -config capture.conf
The environment variable NC_DATABASE_SOURCE can be used to overwrite the default path for the resolver databases /usr/local/etc/netcap/db. Read more about the resolvers package here: