You generated an SSH key pair on your laptop and want passwordless logins to the server web01. Which file has to change, and on which machine?
LPIC-1 Exam 102-500, objective 110. Security easy
Draft — not checked yet. This question was written from the published exam objectives and cites the clause it comes from, but nobody has yet read it against that clause and signed for it.
It is kept out of search results and out of mock exams until they have. Read the source below before you take the answer as settled.
The options
Not correct Copy the private key ~/.ssh/id_ed25519 from the laptop into ~/.ssh/authorized_keys on web01.
Wrong, and a serious mistake. A private key never leaves the machine that generated it, and authorized_keys holds public keys only.
Not correct Append web01's host key to ~/.ssh/authorized_keys on the laptop.
Wrong. The server's host key is recorded by the client in ~/.ssh/known_hosts, and it exists so the client can verify the server. It plays no part in authenticating you to the server.
Correct Append the public key ~/.ssh/id_ed25519.pub from the laptop to ~/.ssh/authorized_keys in your account on web01.
Correct. authorized_keys lives on the machine you log in to and lists the public keys permitted to authenticate as that account. ssh-copy-id automates exactly this append.
Not correct Append the laptop's public key to ~/.ssh/known_hosts on web01.
Wrong. known_hosts is the client-side record of the host keys of servers already contacted; it is consulted to detect a changed or spoofed server, never to authorise a user.
Why
Remember which file lives where. authorized_keys is on the server and answers 'which users may log in as this account'. known_hosts is on the client and answers 'have I seen this server's host key before'. The server's own host key pairs are in /etc/ssh/ssh_host_*_key, and it is their fingerprint you are shown on a first connection. `ssh-copy-id user@web01` does the append and fixes the permissions in one step.
Where this comes from
- Cited
- LPI exam objective 110.3
- What it says
- Configure public key authentication with authorized_keys and understand known_hosts.
Practise this
Reading one question is not practice. The trainer will draw a set from objective 110 and space the ones you get wrong.