fwknopd command not found
Introduction
When you run more command in linux terminal / console, you get the following error message
fwknopd: command not found
or when using sudo you get the following error message
sudo: fwknopd: command not found
Solutions to fwknopd: command not found
How To Fix fwknopd: command not found in Ubuntu / Debian / Kali Linux / Raspbian
In Ubuntu fwknopd is provided by fwknop-server package.
fwknop-server is:
The FireWall KNock OPerator implements an authorization scheme called Single Packet Authorization (SPA), based on Netfilter and libpcap.
Its main application is to protect services such as OpenSSH with an additional layer of security in order to make the exploitation of vulnerabilities (both 0-day and unpatched code) much more difficult.
The authorization server passively listens for authorization packets via libpcap, thus preventing any connections from being processed on the traditional port. Access to a protected service is only granted after a valid encrypted and non-replayed packet is detected.
To fix this problem, we can install more using the command below.
sudo apt-get -y install fwknop-server
This command might take some time to finish depending on your machine internet connection.
You can also use apt command to install fwknop-server.
sudo apt -y install fwknop-server
Or if you have aptitude installed you can use the following command.
sudo aptitude install fwknop-server
Summary
In this tutorial we learn how to fix fwknopd command not found error in Ubuntu / Debian / Kali Linux or Raspbian distribution.