darkstat
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darkstat(8) darkstat(8)
NAME
darkstat - network statistics gatherer
SYNOPSIS
darkstat [ -i interface ] [ -r file ] [ --pppoe ] [ --verbose ] [
--no-daemon ] [ --no-promisc ] [ --no-dns ] [ --no-macs ] [ -p port ] [
-b bindaddr ] [ -f filter ] [ -l network/netmask ] [ --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 ]
DESCRIPTION
darkstat is a packet sniffer that runs as a background process on a
cable/DSL router, 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) cap-
ture file. This is only useful for development and benchmark-
ing. The -r and -i arguments are mutually exclusive.
--pppoe
Don't use this.
Instead, capture on the tunnel interface that your PPPoE soft-
ware 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.
--verbose
Print debugging messages to the terminal.
--no-daemon
Do not detach from the controlling terminal; stay in the fore-
ground.
--no-promisc
Do not use promiscuous mode to capture. Note that an interface
may already be in promiscuous mode. If this is a problem, use
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 resolving.
--no-macs
Do not display MAC addresses in 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.
-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(1) 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.
--chroot dir
Force darkstat to chroot() into the specified directory. With-
out 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 implica-
tions; if you are uncomfortable with this, do not use the --day-
log functionality.
If the daylog argument is not specified, no logging is per-
formed.
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, and upon receiving SIGUSR1, 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 uncom-
fortable 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 ta-
ble. This is used to limit how much accounting data will be
kept in memory.
--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.
--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.
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 network internal traffic:
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(1) man-
page)
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 gate-
way server (which is running darkstat):
darkstat -i fxp0 -l 192.168.1.0/255.255.255.0
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-mem-
ory database. If an --export file was set, it will first save the
database to file.
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 deter-
mined by getting the IP address of the interface you're sniffing on.
You can use the -l argument to override the local address for account-
ing purposes. You can also use it to do accounting for a whole subnet
by specifying an appropriate netmask.
SEE ALSO
tcpdump(1)
HISTORY
darkstat was written in 2001, largely as a result of a certain Aus-
tralian cable Internet provider introducing a 3GB monthly traffic
limit.
AUTHORS
Emil Mikulic and others. (see the AUTHORS and THANKS files)
WEBSITE
http://dmr.ath.cx/net/darkstat/
darkstat 3 September 2008 darkstat(8)
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