Having trouble installing Claude Code plugins on Ubuntu Linux?

If you are getting errors when installing Claude Code plugins from Github due to SSH verification errors (like I did, with some plugins), this might fix it for you.

Adding and Verifying GitHub’s SSH Host Key

When connecting to GitHub via SSH for the first time, you can manually add GitHub’s host key to your known_hosts file and verify that it matches GitHub’s published fingerprint.

1. Add GitHub’s ED25519 Host Key

ssh-keyscan -t ed25519 github.com >> ~/.ssh/known_hosts

This command:

• Connects to github.com
• Retrieves GitHub’s public ED25519 SSH host key
• Appends it to your local ~/.ssh/known_hosts file

This helps SSH recognize GitHub in future connections and prevents repeated trust prompts.

2. Verify the Retrieved Key

ssh-keyscan -t ed25519 github.com | ssh-keygen -lf -

Example output:

256 SHA256:+DiY3wvvV6TuJJhbpZisF/zLDA0zPMSvHdkr4UvCOqU github.com (ED25519)

This displays the fingerprint of the key retrieved from GitHub.

3. Compare Against GitHub’s Official Fingerprints

Check GitHub’s published SSH fingerprints and confirm that the fingerprint shown by your command matches the official value.

GitHub SSH fingerprints:

https://docs.github.com/en/authentication/keeping-your-account-and-data-secure/githubs-ssh-key-fingerprints

Why Verify?

Host key verification protects against man-in-the-middle attacks. If the fingerprint you retrieved matches GitHub’s published fingerprint, you can be confident that you’re connecting to GitHub’s servers and not an impersonator.