Provided by: darkstat_3.0.719-1build1_amd64 
NAME
darkstat - network statistics gatherer
SYNOPSIS
darkstat [ -i interface ] [ -r file ] [ --snaplen bytes ] [ --pppoe ] [ --syslog ] [
--verbose ] [ --no-daemon ] [ --no-promisc ] [ --no-dns ] [ --no-macs ] [ --no-lastseen ]
[ -p port ] [ -b bindaddr ] [ --base path ] [ -f filter ] [ -l network/netmask ] [
--local-only ] [ --chroot dir ] [ --user username ] [ --daylog filename ] [ --import
filename ] [ --export filename ] [ --pidfile filename ] [ --hosts-max count ] [
--hosts-keep count ] [ --ports-max count ] [ --ports-keep count ] [ --highest-port port ]
[ --wait secs ] [ --hexdump ]
DESCRIPTION
darkstat is a packet sniffer that runs as a background process, gathers all sorts of
statistics about network usage, and serves them over HTTP.
All settings are passed on the commandline.
OPTIONS
-i interface
Capture traffic on the specified network interface. This is the only mandatory
commandline argument.
-r file
Instead of capturing live traffic, read it from a pcap(3) capture file. This is
only useful for development and benchmarking. The -r and -i arguments are mutually
exclusive.
--snaplen bytes
How many bytes to capture from the start of each packet. You should not need to
specify this; darkstat will calculate it automatically.
--pppoe
Don't use this.
Instead, capture on the tunnel interface that your PPPoE software provides, for
example tun0 on FreeBSD, pppoe0 on OpenBSD or NetBSD.
If you really must, you can capture on an Ethernet interface and pass this argument
to have darkstat decode PPPoE frames and ignore everything else. Make sure you
also specify your local address with the -l argument!
--syslog
Errors, warnings, and verbose messages will go to syslog (facility daemon, priority
debug) instead of stderr.
On some systems, these messages end up in /var/log/debug by default.
--verbose
Produce more verbose debugging messages.
--no-daemon
Do not detach from the controlling terminal; stay in the foreground.
--no-promisc
Do not use promiscuous mode to capture. Note that an interface may already be in
promiscuous mode, or may later enter promiscuous mode, due to circumstances beyond
darkstat's control. If this is a problem, use -f to specify an appropriate bpf(4)
filter.
--no-dns
Do not resolve IPs to host names. This can significantly reduce memory footprint
on small systems as an extra process is created for DNS resolution.
--no-macs
Do not display MAC addresses in the hosts table.
--no-lastseen
Do not display the last seen time in the hosts table.
-p port
Bind the web interface to the specified port. The default is 667.
-b bindaddr
Bind the web interface to the specified address. The default is to listen on all
interfaces.
--base path
Specify the path of the base URL. This can be useful if darkstat is accessed via a
reverse proxy.
For example, if you use Apache's mod_proxy and want to avoid a complicated setup
with mod_proxy_html (and mod_header to unset the Accept-Encoding header), just set
the base path to something like stats and use a config similar to the following
snippet:
ProxyPass /stats/ http://localhost:667/stats/
ProxyPassReverse /stats/ http://localhost:667/stats/
The default is / (i.e. the root).
-f filter
Use the specified filter expression when capturing traffic. The filter syntax is
beyond the scope of this manual page; please refer to the tcpdump(8) documentation.
-l network/netmask
Define a "local network" according to the network and netmask addresses. All
traffic entering or leaving this network will be graphed, as opposed to the default
behaviour of only graphing traffic to and from the local host.
The rule is that if ip_addr & netmask == network, then that address is considered
local. See the usage example below.
--local-only
Make the web interface only display hosts on the "local network." This is intended
to be used together with the -l argument.
--chroot dir
Force darkstat to chroot() into the specified directory. Without this argument, a
default directory will be used, which is determined at build time. Usually
/var/empty or /var/lib/empty.
For security reasons, this directory should be empty, and the user that darkstat is
running as should not have write access to it.
However, if you wish to use --daylog or --export, darkstat will need write access
to the chroot. If you are uncomfortable with the security implications, don't use
any functionality that requires write access.
--user username
Force darkstat to drop privileges to the uid and gid of the specified user.
Without this argument, a default value will be used, which is set at build time.
Usually nobody.
For security reasons, this should not be root.
--daylog filename
Log daily traffic statistics into the named file, relative to the chroot directory.
If you wish to use --daylog, you must first specify a --chroot directory, and it
must be writeable by the darkstat user. A writeable chroot has security
implications; if you are uncomfortable with this, do not use the --daylog
functionality.
If the daylog argument is not specified, no logging is performed.
The daylog format is:
localtime|time_t|bytes_in|bytes_out|pkts_in|pkts_outs
Lines starting with a # are comments stating when logging started and stopped.
--import filename
Upon starting, import a darkstat database from the named file, relative to the
chroot directory. If you wish to use --import, you must first specify a --chroot
directory. If the import is unsuccessful, darkstat will start with an empty
database.
--export filename
On shutdown, or upon receiving SIGUSR1 or SIGUSR2, export the in-memory database to
the named file, relative to the chroot directory. If you wish to use --export, you
must first specify a --chroot directory, and it must be writeable by the darkstat
user. A writeable chroot has security implications - if you are uncomfortable with
this, do not use the --export functionality.
--pidfile filename
Creates a file containing the process ID of darkstat. This file will be unlinked
upon clean shutdown. As with all pidfiles, if darkstat dies uncleanly, a stale
pidfile can be left over.
For example, start darkstat with:
darkstat -i fxp0 --chroot /var/run/darkstat --pidfile darkstat.pid
And stop with:
kill `cat /var/run/darkstat/darkstat.pid`
By default, kill(1) will send SIGTERM, which will cause darkstat to shut down
cleanly.
--hosts-max count
The maximum number of hosts that will be kept in the hosts table. This is used to
limit how much accounting data will be kept in memory. The number of --hosts-max
must be greater than --hosts-keep
--hosts-keep count
When the hosts table hits --hosts-max and traffic is seen from a new host, we clean
out the hosts table, keeping only the top --hosts-keep number of hosts, sorted by
total traffic.
--ports-max count
The maximum number of ports that will be tracked for each host. This is used to
limit how much accounting data will be kept in memory. The number of --ports-max
must be greater than --ports-keep
--ports-keep count
When a ports table fills up, this many ports are kept and the rest are discarded.
--highest-port port
Ports that are numerically higher than this will not appear in the per-host ports
tables, although their traffic will still be accounted for. This can be used to
hide ephemeral ports. By default, all ports are tracked.
--wait secs
Don't use this. It's a hack to help victims of NetworkManager and similar systems.
You should start darkstat after the capture interface has come up. If you can't,
specifying the --wait option will make darkstat sleep up to the specified number of
seconds for the interface to become ready. Zero means wait indefinitely.
--hexdump
Show hex dumps of received traffic. This is only for debugging, and implies
--verbose and --no-daemon.
USAGE EXAMPLES
To gather statistics on the fxp0 interface:
darkstat -i fxp0
We want to account for traffic on the Internet-facing interface, but only serve web pages
to our private local network where we have the IP address 192.168.0.1:
darkstat -i fxp0 -b 192.168.0.1
We want to serve web pages on the standard HTTP port:
darkstat -i fxp0 -p 80
We are on Optus (cable) and don't want to account for the constant ARP traffic we are
receiving:
darkstat -i fxp0 -f "not arp"
We only want to account for SSH traffic:
darkstat -i fxp0 -f "port 22"
We don't want to account for traffic between internal IPs:
darkstat -i fxp0 -f "not (src net 192.168.0 and dst net 192.168.0)"
(For a full reference on filter syntax, refer to the tcpdump(8) manpage)
We have a network consisting of a gateway server (192.168.1.1) and a few workstations
(192.168.1.2, 192.168.1.3, etc.) and we want to graph all traffic entering and leaving the
local network, not just the gateway server (which is running darkstat):
darkstat -i fxp0 -l 192.168.1.0/255.255.255.0
On some systems, we can't capture on a "decoded" interface but only on nas0 which returns
PPPoE encapsulated packets. Do PPPoE decoding, and override the local IP manually since
it cannot be automatically detected. Note the /32 netmask:
darkstat -i nas0 --pppoe -l 192.168.1.1/255.255.255.255
SIGNALS
To shut darkstat down cleanly, send a SIGTERM or SIGINT signal to the darkstat parent
process.
Sending the SIGUSR1 signal will cause darkstat to empty out its in-memory database. If an
--export file was set, it will first save the database to file. Sending SIGUSR2 will save
the database without emptying it.
FREQUENTLY ASKED QUESTIONS
How many bytes does each bar on the graph represent?
Hover your mouse cursor over a bar and you should get a tooltip saying exactly how many
bytes in and out the bar represents.
Why aren't there labels / tics / a scale on the graphs?
Because implementing them is hard. And doing so correctly, and in a way that works across
all browsers, looks pretty much impossible.
I might attempt it some day. In the meantime, patches would be gladly accepted.
Why are the graphs blank? All the bars are zero.
The graphs only show traffic in/out of the local host, which is determined by getting the
IP address of the interface you're sniffing on.
You can use the -l argument to override the local address for accounting purposes. You
can also use it to do accounting for a whole subnet by specifying an appropriate netmask.
SEE ALSO
tcpdump(8)
HISTORY
darkstat was written in 2001, largely as a result of a certain Australian cable Internet
provider introducing a 3GB monthly traffic limit.
AUTHORS
Emil Mikulic and others. (see the AUTHORS file)
WEBSITE
https://unix4lyfe.org/darkstat/