Ssh (OpenSSH client)

ssh is the OpenSSH ssh client for logging or executing commands into remote devices/machines

     ssh [-46AaCfGgKkMNnqsTtVvXxYy] [-B bind_interface] [-b bind_address] [-c cipher_spec] [-D [bind_address:]port]
        [-E log_file] [-e escape_char] [-F configfile] [-I pkcs11] [-i identity_file] [-J destination] [-L address]
        [-l login_name] [-m mac_spec] [-O ctl_cmd] [-o option] [-p port] [-Q query_option] [-R address] [-S ctl_path]
        [-W host:port] [-w local_tun[:remote_tun]] destination [command]

-X Enables X11 forwarding

ssh -V

Windows: Settings > Apps and click “Manage optional features” under Apps & features.

Configuration

• Configuration file: ~/.ssh/config

Usage

• ssh REMOTE_USERNAME@REMOTE_SERVER_NAME_OR_IP
• ssh -vvv REMOTE_USERNAME@REMOTE_SERVER_NAME_OR_IP (-v increase verbosity, maximum 3)
  • ssh -vvv REMOTE_USERNAME@REMOTE_SERVER_NAME_OR_IP 2>&1 | grep "STRING_TO_SEARCH"

Execute a remote command:

• ssh USERNAME@SERVER_NAME '/path/to/remote/scripts/backup.sh'

• ssh -Q kex SERVER

Multiplexing options

ssh -O check server.example.org or ssh -O check username@server.example.org 
Master running (pid=26289)

ssh -O check username@server.example.org 
Control socket connect(/path/): No such file or directory

To stop an specific multiplexed session:

ssh -O stop username@server.example.org

Avoid using Multiplexing for a connections:

ssh -o "ControlMaster=no" server.example.org

See also: Configure OpenSSH to reuse ssh connections

Logs

ssh -i id_ed25519_xxxxx.pub SERVER_NAME
Load key "id_ed25519_xxxxx.pub": invalid format
Solution:
Use private key instead of public key 
ssh -i id_ed25519_xxxxx SERVER_NAME

• Unable to negotiate with (KexAlgorithms)

Activities

• Understand differences between stop and exit: ssh -O exit username@server.example.org
• Configure OpenSSH to reuse ssh connections
• Execute a command in parallel by ssh

See also

• OpenSSH (changelog), /etc/ssh/sshd_config, /etc/ssh/ssh_config, ~/.ssh/, openSSL, sshd logs, sftp, scp, authorized_keys, ssh-keyscan, ssh-add, ssh-keygen, ssh, Ssh -O stop
• ncat
• tmux, screen, tmate, Byobu, iTerm2, xterm, reptyr, disown, coolterm, minicom
• ssh clients: ssh (OpenSSH client), putty, plink, mosh, paramiko, conch pssh, sshpass and autossh

http://man7.org/linux/man-pages/man1/ssh.1.html

https://stackoverflow.com/a/48330113