step 1. 

ssh-keygen

step 2.

ssh-copy-id -i ~/.ssh/id_rsa.pub root@192.168.1.100

step 3.

ssh root@192.168.1.100

远程执行命令 

ssh root@192.168.1.100 "df -h"

多条

ssh root@192.168.1.100 "pwd; cat hello.txt"