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. ...

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 or ...

in which a stable release of

computer software Software consists of computer programs that instruct the Execution (computing), execution of a computer. Software also includes design documents and specifications. The history of software is closely tied to the development of digital comput ...

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 Software, computer software that is released under a Open-source license, license in which the copyright holder grants users the rights to use, study, change, and Software distribution, distribute the software an ...

, where it describes a software edition that is supported for months or years longer than the software's standard edition. This is often called an extended-support release. ''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 Reliability engineering is a sub-discipline of systems engineering that emphasizes the ability of equipment to function without failure. Reliability is defined as the probability that a product, system, or service will perform its intended functi ...

to the

software development process In software engineering, a software development process or software development life cycle (SDLC) is a process of planning and managing software development. It typically involves dividing software development work into smaller, parallel, or s ...

and

software release life cycle The software release life cycle is the process of developing, testing, and distributing a software product (e.g., an operating system). It typically consists of several stages, such as pre-alpha, alpha, beta, and release candidate, before the fi ...

. Long-term support extends the period of

software maintenance Software maintenance is the modification of software after delivery. Software maintenance is often considered lower skilled and less rewarding than new development. As such, it is a common target for outsourcing or offshoring. Usually, the tea ...

; 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 environ ...

, expense, and disruption of software deployment, while promoting the dependability of the software. It does not necessarily imply

technical support Technical support, commonly shortened as tech support, is a customer service provided to customers to resolve issues, commonly with consumer electronics. This is commonly provided via call centers, online chat and email. Many companies provid ...

. At the beginning of a long-term support period, the

software developer Software development is the process of designing and Implementation, implementing a software solution to Computer user satisfaction, satisfy a User (computing), user. The process is more encompassing than Computer programming, programming, wri ...

s impose a feature freeze: They make patches to correct

software bug A software bug is a design defect ( bug) in computer software. A computer program with many or serious bugs may be described as ''buggy''. The effects of a software bug range from minor (such as a misspelled word in the user interface) to sev ...

s and

vulnerabilities Vulnerability refers to "the quality or state of being exposed to the possibility of being attacked or harmed, either physically or emotionally." The understanding of social and environmental vulnerability, as a methodological approach, involves ...

, but do not introduce new features that may cause regression. The software maintainer either distributes patches individually, or packages them in maintenance releases, point releases, 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 decision-maker 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 software publisher 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 discipli ...

. 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 and administrators 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 or that reduce IT risk (such as security patches). 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 software that have a specific LTS version in addition to a normal release cycle. Many projects, such as

CentOS CentOS (, from Community Enterprise Operating System; also known as CentOS Linux) is a discontinued Linux distribution that provided a free and open-source community-supported computing platform, functionally compatible with its upstream (softw ...

, provide a long period of support for every release. :1. The support period for Ubuntu's parent distribution,

Debian Debian () is a free and open-source software, free and open source Linux distribution, developed by the Debian Project, which was established by Ian Murdock in August 1993. Debian is one of the oldest operating systems based on the Linux kerne ...

, 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