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This page expects that you've followed this guide
Use the keypair created in Horizon
When you create a keypair in Horizon (the web GUI), you will end up with dowloading a .pem file. This file can not be used in PuTTy directly, and has to be converted to a format that PuTTy undertandsunderstands.
Open puttygen, and select File -> Load private key
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The .ppk you now have generated, can be used with PuTTy to connect to your virtual machines.
Import a keypair generated with puttygen
If you already have generated a keypair with puttygen, that you want to import into SkyHiGh, you will need to extract the public key in OpenSSH format.
Open puttygen, and load your existing .ppk file (following the steps above)
Copy the content in the textbox Public key for pasting into OpenSSH authorized_keys file. This content should be pasted into Horizon in this step.
Your existing keypair should now be available in SkyHiGh, and you can use your existing .ppk when connecting to your virtual Linux Machine.