Check last | grep reboot
. This will show you a list of boot times. On my Ubuntu 11.04 installation, this produces lines like:
reboot system boot 2.6.38-13-generi Wed Dec 28 12:42 - 15:37 (1+02:55)
reboot system boot 2.6.38-13-generi Tue Dec 27 07:33 - 15:37 (2+08:03)
reboot system boot 2.6.38-13-generi Sat Dec 24 14:43 - 23:14 (2+08:31)
reboot system boot 2.6.38-13-generi Fri Dec 23 11:07 - 16:29 (05:22)
reboot system boot 2.6.38-13-generi Thu Dec 22 21:05 - 16:29 (19:23)
These mean that my system is up for
- 1 day, 2 hours, 55 minutes
- 2 days, 8 hours, 3 minutes
- 2 days, 8 hours, 31 minutes
- 5 hours 22 minutes
- 19 hours 23 minutes
Hopefully Ubuntu 8.04 has the same feature.