John the Ripper is a program for recovering passwords from their hashes.
The program installation command in Ubuntu/Debian:
sudo apt-get install john
Here is an example of john running to guess passwords at random (the longest method):
john file.txt
Where file.txt is a file with a password hash in the form of login:hash, if there are several passwords, then they can be written in a column.
An example of a simple launch, to select a password similar to login:
john -single file.txt
An example of john running to select a password using 26 characters (from “a” to “z”):
john -i:alpha file.txt
You can specify: alpha – only letters, digits – only numbers, lanman – letters, numbers and some characters, all – all.
Dictionary search (where list.txt is a file with a password dictionary):
john -w:list.txt file.txt