Uptime

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Uptime is a measure of the time a computer system has been "up" and running. It came into use to describe the opposite of downtime, times when a system was non-operational. The uptime and reliability of computer and communications facilities is sometimes measured in nines. "Five nines" means 99.999% reliability, which translates to a total downtime of no longer than five minutes per year.

It is often used as a measure of computer operating system reliability and stability, in that this time represents the time a computer can be left unattended without crashing, or needing to be rebooted for administrative or maintenance purposes. Long uptime can also indicate negligence as many critical updates require reboot on some operating systems.

The uptime(1) command on Unix systems will show the current time, the uptime, the number of users and load averages for the past 1, 5 and 15 minute intervals.

$ uptime
3:23PM  up 1337 days, 15:55, 2 users, load averages: 0.11, 0.12, 0.12

The Uptime-Project collects data on uptimes from users, and the current record for longest uptime is 6 years, 98 days, 12 hours, 6 minutes and 44 seconds on a computer running SunOS 5.6. ^[1] The uptime of a personal computer is sometimes displayed as a badge of honour on an email signature or web site/forum. This was especially true in the Windows 9x days, where GNU/Linux, Windows NT and Windows 2000 users would boast of uptimes of more than 30 days, whereas many real-world Windows 9x installations crashed at least once a day. In more recent times very long uptimes for home users with Unix, Windows NT and Windows 2000 machines are less striking because the Windows 9x line has been replaced by the Windows NT-based Windows XP.

Netcraft maintains the uptime records for many thousands of web hosting computers.

Users of Windows XP Professional systems need to type systeminfo at the command prompt to display all system information, including the System Up Time.

[edit] Notes

^ Uptime Project - Toplist: Records. Retrieved on 2006-04-30.

[edit] See also

Myth of the nines for a discussion of downtime and availability
High availability
Downtime
List of Unix programs

[edit] External links

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