Background
A client might provide you with a .ppk file, which is typically used with Putty and SSH connections. If, however, you are using Ubuntu or CentOS, you will need the key in .pem format. This article explains how to quickly convert said .ppk file to .pem file.
Steps to convert a .ppk file to a .pem file
Follow these simple steps:
sudo apt-get install putty-tools puttygen file.ppk -O private-openssh -o file.pem
Now file.pem is converted! To use it, remember to change the permissions to r first and then specify the new .pem file on the command line when connecting:
chmod 400 file.pem ssh -i file.pem [email protected]
Reference
man puttygen produces:
puttygen ( keyfile | -t keytype [ -b bits ] )
[ -C new-comment ] [ -P ] [ -q ]
[ -O output-type | -l | -L | -p ]
[ -o output-file ]