There are a few commands you can use, "uptime" gives basic information on how long the system has been up and the average load; "w" gives the same as "uptime" but also provides information on who is logged in and what they're doing (the w is for who); "cat /proc/uptime" shows how long the system has been running, in seconds.
Here's some examples of what they look like:
Code:
andy@linux> uptime
1:55pm up 21 days 20:49, 2 users, load average: 0.50, 0.27, 0.21
Code:
andy@linux> w
13:55:56 up 21 days, 20:49, 2 users, load average: 0.46, 0.27, 0.21
USER TTY LOGIN@ IDLE JCPU PCPU WHAT
andy tty4 10Jan06 22:41 5.46s 0.07s vim
andy :0 10Jan06 ?xdm? 2days 0.02s /bin/sh /opt/kde3/bin/startkde
Code:
andy@linux> cat /proc/uptime
1889367.47 1782617.72