02 / Networking

A small SSH key checklist.

Check the destination, the identity, and the permissions before changing authentication settings.

2 MIN READ · A PRACTICAL FIELD NOTE

See the effective configuration

ssh -G your-host

This prints the configuration after matching the host entry. Check hostname, user, port, and identityfile. An alias may select options that differ from the defaults.

Inspect the agent

ssh-add -l

The command lists fingerprints for keys loaded into the current agent. Compare the expected public-key fingerprint with the one you intend to use. A private key should stay on the client that owns it.

Check ownership and access

The account's SSH directory and authorized_keys must have suitable ownership and permissions. Common settings are 700 for ~/.ssh and 600 for authorized_keys. Check the existing files rather than changing permissions recursively.

Test a second connection

ssh -v -o IdentitiesOnly=yes -i ~/.ssh/your_key your-user@your-host

Verbose output helps explain which key is offered and why authentication stops. Treat the output as connection information and review it before sharing.

Further reading: The OpenSSH client manual.