Uptime is a measure of system reliability, expressed as the period of time a machine, typically a computer, has been continuously working and available. Uptime is the opposite of downtime.
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]
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]
A Cisco router had been reported to have been running continuously for 21 years as of 2018. [6] As of April 11, 2023, the uptime had increased to 26 years, 25 weeks, 1 day, 1 hour, and 8 minutes until the router was later decommissioned and the final report of the uptime was 26 years, 28 weeks, 2 days, and 6 minutes. [7] [8]
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).
The output of the systeminfo
command includes a "System Up Time" [9] 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 are 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.[ citation needed ]
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
. [10] 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
Uptime can be determined via Windows Management Instrumentation (WMI), by querying the LastBootUpTime
property of the Win32_OperatingSystem
class. [11] At the command prompt, this can be done using the wmic
command:
C:\>wmic os get lastbootuptime LastBootUpTime20110508161751.822066+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. [12] [13]
Microsoft formerly provided a downloadable utility called Uptime.exe
, which reports elapsed time in days, hours, minutes, and seconds. [14]
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 drift forward every time the computer sleeps or hibernates.[ citation needed ]
The uptime
command is also available for FreeDOS. The version was developed by M. Aitchison. [15]
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
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. [16] On multi-core systems (and some Linux versions) the second number is the sum of the idle time accumulated by each CPU. [17]
BSD-based operating systems such as FreeBSD, Mac OS X, and SySVr4 have the uptime command (See – FreeBSD General Commands Manual).
$ uptime 3:01AM up 69 days, 7:53, 0 users, load averages: 0.08, 0.07, 0.05
The uptime program on BSD is a hard link to the w program. [18] The w program is based on the RSTS/E, TOPS-10, and TOPS-20 SYSTAT program. [19]
There is also a method of using sysctl to call the system's last boot time: [20]
$ sysctlkern.boottime kern.boottime: { sec = 1271934886, usec = 667779 } Thu Apr 22 12:14:46 2010
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. [21]
$ showsystem/noprocess OpenVMS V7.3-2 on node JACK 29-JAN-2008 16:32:04.67 Uptime 894 22:28:52
The command output above shows that node JACK on 29 January 2008 at 16:32:04.67 has an uptime of 894 days 22 hours 28 minutes and 52 seconds.
NT File System (NTFS) is a proprietary journaling file system developed by Microsoft in the 1990s.
Novell, Inc. was an American software and services company headquartered in Provo, Utah, that existed from 1980 until 2014. Its most significant product was the multi-platform network operating system known as Novell NetWare. Novell technology contributed to the emergence of local area networks, which displaced the dominant mainframe computing model and changed computing worldwide.
In computing, the superuser is a special user account used for system administration. Depending on the operating system (OS), the actual name of this account might be root, administrator, admin or supervisor. In some cases, the actual name of the account is not the determining factor; on Unix-like systems, for example, the user with a user identifier (UID) of zero is the superuser [i.e., uid=0], regardless of the name of that account; and in systems which implement a role-based security model, any user with the role of superuser can carry out all actions of the superuser account. The principle of least privilege recommends that most users and applications run under an ordinary account to perform their work, as a superuser account is capable of making unrestricted, potentially adverse, system-wide changes.
The year 2038 problem is a time computing problem that leaves some computer systems unable to represent times after 03:14:07 UTC on 19 January 2038.
A live CD is a complete bootable computer installation including operating system which runs directly from a CD-ROM or similar storage device into a computer's memory, rather than loading from a hard disk drive. A live CD allows users to run an operating system for any purpose without installing it or making any changes to the computer's configuration. Live CDs can run on a computer without secondary storage, such as a hard disk drive, or with a corrupted hard disk drive or file system, allowing data recovery.
In computing, a loadable kernel module (LKM) is an object file that contains code to extend the running kernel, or so-called base kernel, of an operating system. LKMs are typically used to add support for new hardware and/or filesystems, or for adding system calls. When the functionality provided by an LKM is no longer required, it can be unloaded in order to free memory and other resources.
fdisk is a command-line utility for disk partitioning. It has been part of DOS, DR FlexOS, IBM OS/2, and early versions of Microsoft Windows, as well as certain ports of FreeBSD, NetBSD, OpenBSD, DragonFly BSD and macOS for compatibility reasons. Windows 2000 and its successors have replaced fdisk with a more advanced tool called diskpart.
IPX/SPX stands for Internetwork Packet Exchange/Sequenced Packet Exchange. IPX and SPX are networking protocols used initially on networks using the Novell NetWare operating systems. They also became widely used on networks deploying Microsoft Windows LANs, as they replaced NetWare LANs, but are no longer widely used. IPX/SPX was also widely used prior to and up to Windows XP, which supported the protocols, while later Windows versions do not, and TCP/IP took over for networking.
Unified Extensible Firmware Interface is a specification for the firmware architecture of a computing platform. When a computer is powered on, the UEFI-implementation is typically the first that runs, before starting the operating system. Examples include AMI Aptio, Phoenix SecureCore, TianoCore EDK II, InsydeH2O.
Address space layout randomization (ASLR) is a computer security technique involved in preventing exploitation of memory corruption vulnerabilities. In order to prevent an attacker from reliably redirecting code execution to, for example, a particular exploited function in memory, ASLR randomly arranges the address space positions of key data areas of a process, including the base of the executable and the positions of the stack, heap and libraries.
The Advanced Host Controller Interface (AHCI) is a technical standard defined by Intel that specifies the register-level interface of Serial ATA (SATA) host controllers in a non-implementation-specific manner in its motherboard chipsets.
The GUID Partition Table (GPT) is a standard for the layout of partition tables of a physical computer storage device, such as a hard disk drive or solid-state drive. It is part of the Unified Extensible Firmware Interface (UEFI) standard.
sysctl is a software mechanism in some Unix-like operating systems that reads and modifies the attributes of the system kernel such as its version number, maximum limits, and security settings. It is available both as a system call for compiled programs, and an administrator command for interactive use and scripting. Linux additionally exposes sysctl as a virtual file system.
In computing, sleep is a command in Unix, Unix-like and other operating systems that suspends program execution for a specified time.
Hibernation in computing is powering down a computer while retaining its state. When hibernation begins, the computer saves the contents of its random access memory (RAM) to a hard disk or other non-volatile storage. When the computer is turned on the RAM is restored and the computer is exactly as it was before entering hibernation. Hibernation was first implemented in 1992 and patented by Compaq Computer Corporation in Houston, Texas.
The TCP window scale option is an option to increase the receive window size allowed in Transmission Control Protocol above its former maximum value of 65,535 bytes. This TCP option, along with several others, is defined in RFC 7323 which deals with long fat networks (LFNs).
Hyper-V is a native hypervisor developed by Microsoft; it can create virtual machines on x86-64 systems running Windows. It is included in Pro and Enterprise editions of Windows NT as an optional feature to be manually enabled. A server computer running Hyper-V can be configured to expose individual virtual machines to one or more networks.
A Unix-like operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-like application is one that behaves like the corresponding Unix command or shell. Although there are general philosophies for Unix design, there is no technical standard defining the term, and opinions can differ about the degree to which a particular operating system or application is Unix-like. Some well-known examples of Unix-like operating systems include Linux, FreeBSD and OpenBSD. These systems are often used on servers as well as on personal computers and other devices. Many popular applications, such as the Apache web server and the Bash shell, are also designed to be used on Unix-like systems.
Unix is a family of multitasking, multi-user computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and others. Initially intended for use inside the Bell System, AT&T licensed Unix to outside parties in the late 1970s, leading to a variety of both academic and commercial Unix variants from vendors including University of California, Berkeley (BSD), Microsoft (Xenix), Sun Microsystems (SunOS/Solaris), HP/HPE (HP-UX), and IBM (AIX).
In computing, rebooting is the process by which a running computer system is restarted, either intentionally or unintentionally. Reboots can be either a cold reboot in which the power to the system is physically turned off and back on again ; or a warm reboot in which the system restarts while still powered up. The term restart is used to refer to a reboot when the operating system closes all programs and finalizes all pending input and output operations before initiating a soft reboot.
ln ${DESTDIR}/usr/ucb/w ${DESTDIR}/usr/ucb/uptime
This program is similar to the systat command on Tenex/Tops 10/20