I not joined the "passphrase" twice, then 2 files were generated:
server_1:/home/user/> ssh-keygen -t rsa
I copied id_dsa_pub to the server_2:
Prior backup, renamed it id_rsa.pub:
server_1:/home/user/scp id_rsa.pub user@server_2:/home/user/.ssh/
I grant permission to the new file:
server_2:/home/user/cp -p authorized_keys authorized_keys_bkp server_2:/home/user/mv id_rsa.pub authorized_keys
To try to remove the entries, I tried on both servers:
server_2:/home/user/chmod 644 authorized_keys
without positive results.
ssh-keygen -R hostname
I see the message:
I did not make a backup of known_hosts.
ssh server_2:/home/user: Temporary failure in name resolution
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