root@third:/home/wilma/.ssh/authorized_keys# mv id_rsa.pub ../
root@third:/home/wilma/.ssh/authorized_keys# cd ..
root@third:/home/wilma/.ssh# ls
authorized_keys  id_rsa.pub
root@third:/home/wilma/.ssh# rmdir authorized_keys/
root@third:/home/wilma/.ssh# echo id_rsa.pub >>authorized_keys
-rw-r--r-- 1 wilma wilma 419 Sep 25 02:46 id_rsa.pub
root@third:/home/wilma/.ssh# chown wilma:wilma authorized_keys 
root@third:/home/wilma/.ssh# cd ..
root@third:/home/wilma# chown wilma:wilma .ssh
root@third:/home/wilma# chmod 700 .ssh
root@third:/home/wilma# ls -la
...
drwx------  2 wilma wilma 4096 Sep 25 06:16 .ssh
...
root@third:/home/wilma# cd .ssh/
root@third:/home/wilma/.ssh# chmod 600 authorized_keys 
root@third:/home/wilma/.ssh# exit
logout
Connection to 143.110.153.42 closed.
$ ssh wilma@143.110.153.42
wilma@143.110.153.42: Permission denied (publickey).
$ ssh -v wilma@143.110.153.42
OpenSSH_7.6p1 Ubuntu-4ubuntu0.3, OpenSSL 1.0.2n  7 Dec 2017
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug1: Connecting to 143.110.153.42 [143.110.153.42] port 22.
debug1: Connection established.
debug1: identity file /home/hogan/.ssh/id_rsa type 0
debug1: key_load_public: No such file or directory
debug1: identity file /home/hogan/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/hogan/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/hogan/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/hogan/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/hogan/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/hogan/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/hogan/.ssh/id_ed25519-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_7.6p1 Ubuntu-4ubuntu0.3
debug1: Remote protocol version 2.0, remote software version OpenSSH_8.2p1 Ubuntu-4ubuntu0.1
debug1: match: OpenSSH_8.2p1 Ubuntu-4ubuntu0.1 pat OpenSSH* compat 0x04000000
debug1: Authenticating to 143.110.153.42:22 as 'wilma'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: curve25519-sha256
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:D6XoS17x+bi8QeACsXmMrZeRDV9bOVcPIJ94zP9xZx4
debug1: Host '143.110.153.42' is known and matches the ECDSA host key.
debug1: Found key in /home/hogan/.ssh/known_hosts:2
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<ssh-ed25519,sk-ssh-ed25519@openssh.com,ssh-rsa,rsa-sha2-256,rsa-sha2-512,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,sk-ecdsa-sha2-nistp256@openssh.com>
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Offering public key: RSA SHA256:bBpP0w2TsMSLQyp0qTPPZ0pQFS5SZfRz4aS9S3xHjhA /home/hogan/.ssh/id_rsa
debug1: Authentications that can continue: publickey
debug1: Trying private key: /home/hogan/.ssh/id_dsa
debug1: Trying private key: /home/hogan/.ssh/id_ecdsa
debug1: Trying private key: /home/hogan/.ssh/id_ed25519
debug1: No more authentication methods to try.
wilma@143.110.153.42: Permission denied (publickey).