In many occasions I needed to convert a Putty ppk private key nack to open ssh key to be able to use it directly from a linux box command line. It is fairly simple to do but I always need to look it up so here it is for easy reference :
Install putty using yum in Fedora.
If you are using Ubuntu you need to install putty-tools as well
From the command line give
puttygen xxxxx2.ppk -O private-openssh -o key.ssh
Enter passphrase to load key:
Then log onto your system using
ssh firstname.lastname@example.org -p 8057 -i key.ssh