problem with John the ripper

I have problem with John the ripper. It works fine.

but I have deleted the executable file /usr/bin/john by mistake and then I can not do unshadow command any more to crack the passwords as follow:

[root@localhost ~]# cd john-1.7.6/run
[root@localhost run]# umask 077
[root@localhost run]# unshadow /etc/passwd /etc/shadow > mypasswd2
bash: unshadow: command not found

So what should I do to fix this problem

Why not download it again and follow the instructions in the /doc/INSTALL file contained in the john-1.7.6.tar.gz file?

You “may” not need to reinstall
If you haven’t actually deleted anything, you need to start commands with ./ because they haven’t been installed system-wide… or add the ~/john-1.7.6/run directory to the system path.

So taking your commands you posted above, they SHOULD read:

cd john-1.7.6/run
./umask 077
./unshadow /etc/passwd /etc/shadow > mypasswd2