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Remove an outdated host from known_hosts

cautionSSHalle

Caution: This command changes the system. Understand what it does before you run it.

Adjust the values, the command updates live
user@server
ssh-keygen -R server.example.com

Removes all entries for a host from ~/.ssh/known_hosts, even if the file contains hashed hostnames. Useful when a server has been reinstalled and SSH therefore refuses to connect with a warning. A backup of the old file is saved as known_hosts.old.

Note: Only run this if the key change can be explained. An unexpected change may indicate a man-in-the-middle attack. For a non-standard port, the syntax is [host]:2222.

Also searched as

  • remote host identification has changed fix
  • remove host from known_hosts
  • ssh-keygen -R host

Related one-liners

All in SSH

Show the fingerprint of an SSH key

$ssh-keygen -lf /etc/ssh/ssh_host_ed25519_key.pub
harmlessSSH

Change or set the passphrase of an SSH key

$ssh-keygen -p -f ~/.ssh/id_ed25519_server
cautionSSH

Derive the public key from a private SSH key

$ssh-keygen -y -f ~/.ssh/id_ed25519_server
harmlessSSH

Generate an Ed25519 SSH key pair

$ssh-keygen -t ed25519 -a 100 -C "admin@example.com" -f ~/.ssh/id_ed25519_server
harmlessSSH

Connect to an internal server through a jump host

$ssh -J admin@bastion.example.com webuser@10.0.0.12
harmlessSSH

Copy a directory to another server with tar over SSH

$tar czf - -C /var/www/vhosts/example.com/httpdocs . | ssh webuser@neuserver.example.com "tar xzf - -C /var/www/vhosts/example.com/httpdocs"
cautionSSH

Read first, then run.

The commands on myline.de act directly on servers, files and databases. A wrong path or placeholder can delete data irreversibly or make a server unreachable.

  • All commands are provided without warranty and are not tested on every system.
  • Understand what a command does before running it, and check every placeholder.
  • Make a backup first and, if possible, try it on a test system.
  • You run commands at your own risk. Liability for damages is excluded to the extent permitted by law.