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.
-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.
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.
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 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.
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(1)
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:
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.
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.