Generate Your Keys
Linux
From the remote Linux server:
ssh-keygen
This will generate ~/.ssh/id_rsa and ~/.ssh/id_rsa.pub. You can setup your default identity with:
cp ~/.ssh/id_rsa.pub ~/.ssh/identity.pub
Next we will use a helpful tool to copy our public key to the appropriate location on the target server. The "ssh-copy-id" tool will copy the public key to ~/.ssh/authorized_keys and set the appropriate permissions for us. This can be done manually, if needed.
The general method to copy the public key to the target ESX server's authorized list is using ssh-copy-id:
ssh-copy-id root@[SERVER]
If you don't have the default identity.pub setup, you can specify your public key with:
ssh-copy-id -i ~/.ssh/id_rsa.pub root@[SERVER]
WARNING: Make sure to include 'root@' or it will try to copy to the same user name as you are currently logged in as.
Note, each version of ESX/ESXi has a few adjustments to make it work.
Windows
For Windows servers you will need to use PUTTY and PUTTYgen. Within PUTTYgen, simply click "Generate", move your mouse a lot over the blank area, and wait for the keys to be generated.
The text within the "Public key for pasting into OpenSSH authorized_key file" area is the key that needs to go into the authorized_keys file on your server. Click the "Save private key" button and save this private_key.ppk file to a secure location. This is the key you will load into Putty to connect to the server.
ESXi 5.x
ESXi 5.x looses the keys on reboot unless you take a few extra steps.1. Copy public key:
linux# ssh-copy-id -i ~/.ssh/id_rsa.pub root@[SERVER]
2. On the ESXi server:
esx# cp /.ssh/authorized_keys /etc/ssh/keys-root/authorized_keys
3. Reboot ESXi server, so the script is saved to the boot bank. (Do not power cycle)
esx# reboot
4. Done. Verify passwordless access:
linux# ssh root@[SERVER]
ESXi 4.x
ESXi 4.x looses the keys on reboot unless you take a few extra steps.1. Copy public key:
linux# ssh-copy-id -i ~/.ssh/id_rsa.pub root@[SERVER]
2. On the ESXi server:
esx# cp -r /.ssh /scratch
3. On the ESXi server, add the following to /etc/rc.local:
esx# cp -r /scratch/.ssh /
3. Reboot ESXi server, so the script is saved to the boot bank. (Do not power cycle)
esx# reboot
4. Done. Verify passwordless access:
linux# ssh root@[SERVER]
ESX 4.x
1. Copy public key:linux# ssh-copy-id -i ~/.ssh/id_rsa.pub root@[SERVER]
2. Done. Verify passwordless access:
linux# ssh root@[SERVER]
Setting up ESXi SSH keys for passwordless access can simplify repeated administration from a remote Linux server. Generating an RSA key pair with ssh-keygen and placing the public key in the target server’s authorized_keys file provides a practical approach to key-based authentication. The article also highlights the importance of using the correct root@SERVER format when copying the key to an ESXi host.
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The Windows procedure described in the article uses PuTTY and PuTTYgen to generate and manage the required keys. Saving the private .ppk file securely and placing the generated public key into the OpenSSH authorized_keys file are important parts of the setup. For broader security-focused applications, Network Security Projects for Final Year offers a relevant direction for exploring authentication, secure access, and protection of networked systems.
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