SSH是最常用的工具了，ssh username@ipAddress 即发起到远程主机的访问。随后输入远程机器的密码即可连接，同时，首次连接到远程主机还会要求获得远程主机的公钥，这时必须手动输"yes". 下图是完整的连接过程。
ha@ha-To-be-filled-by-O-E-M:~$ ssh [email protected]
The authenticity of host '192.168.1.5 (192.168.1.5)' can't be established.
ECDSA key fingerprint is SHA256:yIprcaFyxAR7lY/uXm6p6zMfdtXFSfb1DHI+Buf3MQ0.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.1.5' (ECDSA) to the list of known hosts.
[email protected]'s password:
Welcome to Ubuntu 18.04.1 LTS (GNU/Linux 4.15.0-32-generic x86_64)
在自动化运维时，需要在一个脚本里自动连接到远程主机，这时候是没有人等在屏幕前输密码和yes指令的。
自动输入密码可以使用sshpass工具(不是自带工具，可以运行 sudo apt-get install sshpass 安装)。使用示例如下，sshpass可以自动把密码传递给ssh。
sshpass -p <password> ssh <user>@<ipAdd>但是对于首次连接的主机，或者ip地址改变后的主机，还是需要输入yes确认密钥。禁用认证确认步骤可以解决这一问题。
方法一：设置取消严格的key检查
can set the StrictHostKeyChecking option to no on the command line, and/or send the key to a null known_hosts file. You can also set these options in your config file, either for all hosts or for a given set of IP addresses or host names.
ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no
方法二：在配置文件中设置对某些连接的地址的key自动跳过
To disable (or control disabling), add the following lines to the beginning of /etc/ssh/ssh_config.
Host 192.168.0.*
StrictHostKeyChecking no
UserKnownHostsFile=/dev/null
Options:
The Host subnet can be * to allow unrestricted access to all IPs.
Edit /etc/ssh/ssh_config for global configuration or ~/.ssh/config for user-specific configuration.
这样，如果在命令行中取消主机密钥检查，并且用sshpass传递密码，完整的用法就是：
sshpass -p ${password} ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no $user@$IPAddRef:
http://www.freeoa.net/osuport/netmanage/linux-ssh-auto-accept-pub-key-firstime_2567.html