Uptime

Uptime is a measure of system reliability, expressed as the percentage of time a machine, typically a computer, has been working and available. Uptime is the opposite of downtime.

Htop adds an exclamation mark when uptime is longer than 100 days
This article is about uninterrupted system availability. For use in logistics, see Downtime. For enterprise computing, see high availability. For the first half of a double album by the Kleptones, see Uptime / Downtime § Uptime.

It is often used as a measure of computer operating system reliability or 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.

Conversely, long uptime may indicate negligence, because some critical updates can require reboots on some platforms.[1]

Records

In 2005, Novell reported a server with a 6-year uptime.[2][3] Although that might sound unusual, that is actually common when servers are maintained under an industrial context and host critical applications such as banking systems.

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

A server running Novell NetWare has been reported to have been shut down after 16 years of uptime due to a failing hard disk.[4][5]

Determining system uptime

Microsoft Windows

Windows Task Manager
Windows 7 Task Manager Performance tab screenshot.

Some versions of Microsoft Windows include an uptime field in Windows Task Manager, under the "Performance" tab. The format is D:HH:MM:SS (days, hours, minutes, seconds).

systeminfo

The output of the systeminfo command includes a "System Up Time"[6] or "System Boot Time" field.

C:\>systeminfo | findstr "Time:"
System Up Time:            0 Days, 8 Hours, 7 Minutes, 19 Seconds

The exact text and format is dependent on the language and locale. The time given by systeminfo is not reliable. It does not take into account time spent in sleep or hibernation. Thus, the boot time will drift forward every time the computer sleeps or hibernates.

NET command

The NET command with its STATISTICS sub-command provides the date and time the computer started, for both the NET STATISTICS WORKSTATION and NET STATISTICS SERVER variants. The command NET STATS SRV is shorthand for NET STATISTICS SERVER.[7] The exact text and date format is dependent on the configured language and locale.

C:\>NET STATISTICS WORKSTATION | findstr "since"
Statistics since 8/31/2009 8:52:29 PM

Windows Management Instrumentation (WMI)

Uptime can be determined via Windows Management Instrumentation (WMI), by querying the LastBootUpTime property of the Win32_OperatingSystem class.[8] At the command prompt, this can be done using the wmic command:

C:\>wmic os get lastbootuptime
LastBootUpTime
20110508161751.822066+060

The timestamp uses the format yyyymmddhhmmss.nnn, so in the above example, the computer last booted up on 8 May 2011 at 16:17:51.822. The text "LastBootUpTime" and the timestamp format do not vary with language or locale. WMI can also be queried using a variety of application programming interfaces, including VBScript or PowerShell.[9][10]

Uptime.exe

Microsoft formerly provided a downloadable utility called Uptime.exe, which reports elapsed time in days, hours, minutes, and seconds.[11]

C:\>Uptime
SYSTEMNAME has been up for: 2 day(s), 4 hour(s), 24 minute(s), 47 second(s)

The time given by Uptime.exe is not reliable. It does not take into account time spent in sleep or hibernation. Thus, the boot time will drifts forward every time the computer sleeps or hibernates.

FreeDOS

The uptime command is also available for FreeDOS. The version was developed by M. Aitchison.[12]

Linux

Using uptime

Users of Linux systems can use the BSD uptime utility, which also displays the system load averages for the past 1, 5 and 15 minute intervals:

$ uptime
  18:17:07 up 68 days,  3:57,  6 users,  load average: 0.16, 0.07, 0.06

Using /proc/uptime

Shows how long the system has been on since it was last restarted:

$ cat /proc/uptime
  350735.47 234388.90

The first number is the total number of seconds the system has been up. The second number is how much of that time the machine has spent idle, in seconds.[13] On multi core systems (and some Linux versions) the second number is the sum of the idle time accumulated by each CPU.[14]

BSD

Using uptime

BSD-based operating systems such as FreeBSD, Mac OS X and SySVr4 have the uptime command (See uptime(1) – FreeBSD General Commands Manual).

$ uptime
3:01AM  up 69 days,  7:53, 0 users, load averages: 0.08, 0.07, 0.05

Using sysctl

There is also a method of using sysctl to call the system's last boot time:[15]

$ sysctl kern.boottime
kern.boottime: { sec = 1271934886, usec = 667779 } Thu Apr 22 12:14:46 2010

OpenVMS

On OpenVMS systems, the show system command can be used at the DCL command prompt to obtain the system uptime. The first line of the resulting display includes the system's uptime, displayed as days followed by hours:minutes:seconds. In the following example, the command qualifier /noprocess suppresses the display of per-process detail lines of information.[16]

$ show system/noprocess
OpenVMS V7.3-2 on node JACK 29-JAN-2008 16:32:04.67  Uptime  894 22:28:52

See also

References
  1. "How to install multiple Windows updates or hotfixes with only one reboot". Microsoft Knowledge Base. Microsoft. 2018-04-17. Retrieved 2019-07-11.
  2. Dave Kearns (2005-12-01). "Marathon servers". Network World. IDG Communications. Retrieved 2019-07-11.
  3. "Uptime Workhorses: Still Crazy after all these Years". Novell Cool Solutions: Trench. Novell. 12 Jan 2006. Retrieved 2019-07-11.
  4. Peter Bright (2013-03-29). "Epic uptime achievement unlocked. Can you beat 16 years?". Arc Technica. Condé Nast. Retrieved 2019-07-11.
  5. Axatax (2013-03-28). "So long to a valiant companion". Ars OpenForum. Condé Nast. Retrieved 2014-07-26.
  6. Greg Shultz (2005-08-10). "Tracking down uptime in Windows XP". TechRepublic. CBS Interactive. Archived from the original on 2012-07-08. Retrieved 2014-04-22.
  7. Yuval Sinay (2006-10-25). "How to find Windows uptime?". Microsoft Knowledge Base. Microsoft. Retrieved 2014-04-22.
  8. "Win32_OperatingSystem class". Microsoft. 2018-05-30. Retrieved 2019-07-11.
  9. "How Can I Tell if a Server has Rebooted?". Hey, Scripting Guy! Blog. Microsoft. 2004-09-07. Retrieved 2014-04-22.
  10. "How Can I Determine the Uptime for a Server?". Hey, Scripting Guy! Blog. Microsoft. 2005-08-02. Retrieved 2014-04-22.
  11. "Uptime.exe Tool Allows You to Estimate Server Availability with Windows NT 4.0 SP4 or Higher". Microsoft Knowledge Base. Microsoft. 2012-08-20. Archived from the original on 2014-04-24. Retrieved 2014-04-22.
  12. M. Aitchison (1998-04-15). "Package uptime in group Unix-like". Retrieved 2019-07-11.
  13. Marie Doleželová, Mirek Jahoda et al. "/proc/uptime". Deployment Guide - Red Hat Enterprise Linux 6. Red Hat, Inc. Retrieved 2018-12-12.CS1 maint: uses authors parameter (link)
  14. Martin Schwidefsky (2009-05-11). "Re: [PATCH] Re: /proc/uptime idle counter remains at 0". Linux kernel mailing list (Mailing list). Retrieved 2014-04-22.
  15. "Mac OS X Manual Page For sysctl(8)". Mac Dev Center. Apple. 2009-10-15. Archived from the original on 2010-01-14. Retrieved 2014-04-22.
  16. "Undocumented OpenVMS Features". PARSEC Group. 2008-10-29. Archived from the original on 2011-05-11. Retrieved 2014-04-22.
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