Command-line Flags

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

Environment

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.

Configuration File

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 capture
promisc true
​
# don't print infos to stdout
quiet false
​
# reassemble TCP connections
reassemble-connections true
​
# resolve ips to domains via the operating systems default dns resolver
reverse-dns false
​
# use serviceDB for device profiling
serviceDB false
​
# configure snaplen for live capture from interface
snaplen 1514
​
# print netcap package version and exit
version false
​
# wait for all connections to finish processing before cleanup
wait-conns true
​
# number of workers
workers 12
​
# write incomplete response
writeincomplete 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

Resolver Database

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:

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