万物并作，吾以观复。夫物芸芸，各复归其根。 The operation of anything is governed by some rule.
IdentityFile ~/.ssh/id_rsa # “~/.ssh/id_rsa”为默认文件，若使用此默认文件，则可忽略该项
$ ssh dahuilang
$ hwclockto see system clock:
$ dategenerally, the two clocks are not holding the same time value. to synchronize them, normally adjust the system clock firstly and then set the hardware clock according to the system clock time:
$ date +%T -s '18:12:56'
$ hwclock --systohc
$ kill -- -1024`--' prevents a normal argument that starts with a `-' from being interpreted as a switch. see: http://stackoverflow.com/questions/392022/best-way-to-kill-all-child-processes