1.sudo apt-get install putty
2.puttygen private.ppk -o private-key -O private-openssh (Where “private.ppk” is the PuTTY .ppk file to convert, and “private-key” is the name of the converted key file.)
3.ssh -i private-key username@remote-server-ip
Now, you can easily access the remote server using the openssh standard private key:
refurl: https://rbgeek.wordpress.com/2012/11/14/how-to-convert-ppk-file-to-ssh-remote-server-in-ubuntu/
