A common problem for system administrators or daily Linux users is “command not found” error. There are different causes of this problem. We can troubleshoot this problem in several ways.

Misspell Error

Misspelling is number one problem especially novice users or beginners. Here is an example we will try to run nmap command but we will misspell namp like below.

$ namp

In this example, we try to run Nmap but misspelled it. Ubuntu provides some help by listing suggestion about the correct command.

Path Is Not Correct

Path is used to specify commands locations. If command location is not specified in PATH environment variable we can get  an error like “The command could not be located”

$ zip

We can solve this by adding /usr/bin to the PATH environment variable and export it like below.

$ export PATH=$PATH:"/usr/bin"

Not Installed

We generally assume that application is all readily installed. But default installed applications and commands changes from distribution to distribution or release from release

$ aircrack-ng

So we can solve this by installing the given package or tool like below.

$ sudo apt install aircrack-ng