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Cloud & Security · Developer Error Resolution Lab

Fix SSH 'WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED' and 'Host key verification failed'

Safely remove a stale host key from known_hosts after a server rebuild or IP reuse, and verify the new fingerprint before trusting it.

Triggered Error Message:

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @ @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ Host key verification failed.

Customize Solution for Your Environment
# 1. Remove the old key for 203.0.113.10
ssh-keygen -R 203.0.113.10

# 2. Fetch and print the new fingerprint BEFORE trusting it
ssh-keyscan -t ed25519 203.0.113.10 | ssh-keygen -lf -

# 3. If it matches your provider's console / docs, connect
ssh user@203.0.113.10

Root Cause & Mechanism Analysis

Why does this error occur?

The server presented a different host key than the one stored in `~/.ssh/known_hosts`. This is expected after reinstalling a VPS, rebuilding a container, or when a cloud provider reassigns an IP — but it is also exactly what a man-in-the-middle attack looks like.

Frequently Asked Questions

Is it safe to just delete ~/.ssh/known_hosts?
It works but throws away every trusted fingerprint. Use `ssh-keygen -R host` to remove only the changed one.
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