see linux Run Time
1.who -b View the last boot time
$ who -b
system boot 2016-08-27 14:03
2.last reboot View recent restart records
$last reboot
reboot system boot 4.4.0-34-generic Sat Aug 27 14:03 still running
reboot system boot 4.4.0-34-generic Fri Aug 26 10:53 still running
reboot system boot 4.4.0-34-generic Wed Aug 24 10:49 - 10:52 (2+00:03)
reboot system boot 4.4.0-34-generic Tue Aug 23 08:48 - 10:52 (3+02:03)
reboot system boot 4.4.0-34-generic Tue Aug 23 08:03 - 08:48 (00:44)
reboot system boot 4.4.0-34-generic Tue Aug 23 08:03 - 08:48 (00:45)
reboot system boot 4.4.0-34-generic Tue Aug 23 07:59 - 08:03 (00:03)
reboot system boot 4.4.0-34-generic Mon Aug 22 08:33 - 18:16 (09:43)