Long-term support (LTS) is a

product lifecycle management In industry, Product Lifecycle Management (PLM) is the process of managing the entire lifecycle of a product from its inception through the engineering, design and manufacture, as well as the service and disposal of manufactured products. PL ...

policy Policy is a deliberate system of guidelines to guide decisions and achieve rational outcomes. A policy is a statement of intent and is implemented as a procedure or protocol. Policies are generally adopted by a governance body within an orga ...

in which a stable release of

computer software Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work. At the lowest programming level, executable code consists ...

is maintained for a longer period of time than the standard edition. The term is typically reserved for

open-source software Open-source software (OSS) is computer software that is released under a license in which the copyright holder grants users the rights to use, study, change, and distribute the software and its source code to anyone and for any purpose. Op ...

, where it describes a software edition that is supported for months or years longer than the software's standard edition. ''Short term support'' (STS) is a term that distinguishes the support policy for the software's standard edition. STS software has a comparatively short life cycle, and may be afforded new features that are omitted from the LTS edition to avoid potentially compromising the stability or compatibility of the LTS release.

Characteristics

LTS applies the tenets of reliability engineering to the software development process and

software release life cycle A software release life cycle is the sum of the stages of development and maturity for a piece of computer software ranging from its initial development to its eventual release, and including updated versions of the released version to help impro ...

. Long-term support extends the period of software maintenance; it also alters the type and frequency of software updates ( patches) to reduce the

risk In simple terms, risk is the possibility of something bad happening. Risk involves uncertainty about the effects/implications of an activity with respect to something that humans value (such as health, well-being, wealth, property or the environm ...

, expense, and disruption of

software deployment Software deployment is all of the activities that make a software system available for use. The general deployment process consists of several interrelated activities with possible transitions between them. These activities can occur on the ...

, while promoting the

dependability In systems engineering, dependability is a measure of a system's availability, reliability, maintainability, and in some cases, other characteristics such as durability, safety and security. In real-time computing, dependability is the ability to ...

of the software. It does not necessarily imply

technical support Technical support (abbreviated as tech support) is a call centre type customer service provided by companies to advise and assist registered users with issues concerning their technical products. Traditionally done on the phone, technical suppor ...

. At the beginning of a long-term support period, the software developers impose a feature freeze: They make patches to correct software bugs and

vulnerabilities Vulnerability refers to "the quality or state of being exposed to the possibility of being attacked or harmed, either physically or emotionally." A window of vulnerability (WOV) is a time frame within which defensive measures are diminished, com ...

, but do not introduce new features that may cause regression. The

software maintainer In free and open source software and inner source software, a software maintainer or package maintainer is usually one or more people who build source code into a binary package for distribution, commit patches, or organize code in a source rep ...

either distributes patches individually, or packages them in

maintenance release A maintenance release (also minor release or Maintenance Pack or MP) is a release of a product that does not add new features or content. For instance, in computer software, maintenance releases are typically intended to solve minor problems, typi ...

point release A point release (also a dot release) is a minor release of a software project, especially one intended to fix bugs or do small cleanups rather than add significant features. Often, there are too many bugs to be fixed in a single major or minor ...

s, or service packs. At the conclusion of the support period, the product either reaches end-of-life, or receives a reduced level of support for a period of time (e.g., high-priority security patches only).

Rationale

Before upgrading software, a

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might consider the

and cost of the upgrade. As software developers add new features and fix software bugs, they may introduce new bugs or break old functionality. When such a flaw occurs in software, it is called a '' regression''. Two ways that a

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or maintainer can reduce the

of regression are to release major updates less frequently, and to allow users to test an alternate, updated version of the software. LTS software applies these two risk-reduction strategies. The LTS edition of the software is published in parallel with the STS (short-term support) edition. Since major updates to the STS edition are published more frequently, it offers LTS users a preview of changes that might be incorporated into the LTS edition when those changes are judged to be of sufficient

quality Quality may refer to: Concepts *Quality (business), the ''non-inferiority'' or ''superiority'' of something *Quality (philosophy), an attribute or a property *Quality (physics), in response theory * Energy quality, used in various science discipl ...

. While using older versions of software may avoid the risks associated with upgrading, it may introduce the risk of losing support for the old software. Long-term support addresses this by assuring

users Ancient Egyptian roles * User (ancient Egyptian official), an ancient Egyptian nomarch (governor) of the Eighth Dynasty * Useramen, an ancient Egyptian vizier also called "User" Other uses * User (computing) A user is a person who ...

and

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that the software will be maintained for a specific period of time, and that updates selected for publication will carry a significantly reduced risk of regression. The maintainers of LTS software only publish updates that either have low

IT risk Information technology risk, IT risk, IT-related risk, or cyber risk is any risk related to information technology. While information has long been appreciated as a valuable and important asset, the rise of the knowledge economy and the Digital Re ...

or that reduce IT risk (such as

security patch A patch is a set of changes to a computer program or its supporting data designed to update, fix, or improve it. This includes fixing security vulnerabilities and other bugs, with such patches usually being called bugfixes or bug fixes. Patches ...

es). Patches for LTS software are published with the understanding that installing them is less risky than not installing them.

Software with separate LTS versions

This table only lists those have a specific LTS version in addition to a normal release cycle. Many projects, such as CentOS, provide a long period of support for every release. :1. The support period for Ubuntu's parent distribution, Debian, is one year after the release of the next stable version. Since Debian 6.0 "Squeeze", LTS support (bug fixes and security patches) was added to all version releases. The total LTS support time is generally around 5 years for every version. Due to the irregular release cycle of Debian, support times might vary from that average and the LTS support is done not by the Debian team but by a separate group of volunteers.

Characteristics

Rationale

Software with separate LTS versions

See also

References

Further reading