Experimente o comando uptime
,
$ uptime -s
2014-06-17 09:36:38
OR
$ uptime -p
up 10 hours, 12 minutes
De uptime --help
-p, --pretty show uptime in pretty format
-s, --since system up since
De man uptime
,
uptime gives a one line display of the following information. The cur‐
rent time, how long the system has been running, how many users are
currently logged on, and the system load averages for the past 1, 5,
and 15 minutes.