Knockd daemon fails to start

I was trying to setup knockd, a port knocking daemon available to Ubuntu distros.

Before setting up my port knocking sequences, I decided to give a shot to the default knocking sequence, since it should open SSH to my IP address.

But when I first started the service sudo service knockd start, it failed with no error message and the service log located at /var/log/knockd.log is empty.

 * Starting Port-knock daemon knockd  [fail]

No changes have been made to the configuration, with the exception of /etc/default/knock where we have to change START_KNOCKD from 0 to 1.

I'm most puzzled with this since the log file is literally empty.

Any help is appreciated, thank you.

Solution 1:

You can configure it to log to syslog by changing /etc/knockd.conf.

Comment out logfile = /var/log/knockd.log under [options]and add following:

UseSyslog

Then start it from shell and check output:

knockd --debug --verbose

More details here: http://manpages.ubuntu.com/manpages/dapper/man1/knockd.1.html

Solution 2:

knockd might not be finding your non-standard interface.

Specify it in /etc/default/knockd like so:

KNOCKD_OPTS="-i eth0"

Solution 3:

find the interface which case, your ip:

ifconfig

and add him to: /etc/knockd.conf example:

Interface = venet0:0