Long-term support

Long-term support (LTS) is a type of special versions or editions of software designed to be supported for a longer than normal period. It is particularly applicable to open-source software projects.

It is a product lifecycle management policy for computer software, that applies the tenets of reliability engineering to the software development process and software release life cycle. Long-term support extends the period of software maintenance; it also alters the type and frequency of software updates (patches) to reduce the risk, expense, and disruption of software deployment, while promoting the dependability of the software. It does not, however, imply technical support.

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, 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 reaches end-of-life.

The term long-term-support is usually reserved for special versions or editions of software that otherwise has a much shorter release life cycle. Typically, a publisher of LTS software maintains it for at least two years.

Need for long-term support

The traditional software lifecycle in many open source projects is release early, release often, or a regular time-based release schedule. In either case, each new release includes both fixes for security vulnerabilities and new functionality.

Large organisations, or users with mission critical projects, need the security fixes but would often prefer to retain the same base version for an extended period without any new or changed functionality. Their concern is, that as software developers add new features they can accidentally introduce new bugs or break old functionality. While in theory they could backport just the security fixes from each new release to their deployed version, in practise this would often be prohibitively difficult or costly.

Even without the added risks, for these types of users, new functionality is also often expensive. Updating a web application with a sensitive configuration, for example, may require the cooperation of many people: Developers for retrofitting; a database administrator for database schema changes; software testers for regression testing; a project manager for scheduling, liaising, and facilitating; a system administrator or release manager for software deployment oversight; and IT operations personnel for backups, installation, and disaster recovery.

LTS versions of a software package typically address these concerns by releasing only security-related updates for the LTS version - such that installing them should always be 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.

Software	Software type	Date of first LTS release	LTS period	STS period	Notes
Ubuntu	Linux distribution	1 June 2006 (2006-06-01) (v6.06 LTS)	5 years	9 months	A new LTS version is released every two years. From 2006 through 2011, LTS support for the desktop was for approximately two years, and for servers five, but LTS versions are now supported for five years for both.
Trisquel 7.0	Linux distribution	2014-11-04	5 years	1 year	Linux Kernel-libre 3.13, GNOME fallback 3.12 and Abrowser or GNU IceCat
Symfony	Application framework	June 2013 (2013-06)	3 years	8 months
Joomla!	CMS	January 2008 (2008-01) (v1.5)	2 years, 3 months	7 months	Since Joomla! is a web application, long-term support also implies support for legacy web browsers.
Linux Mint	Linux distribution	8 June 2008 (2008-06-08)	5 years	6 months	At version 13 the LTS period increased from three years to five, since Linux Mint derives from Ubuntu.
Linux kernel	Kernel	11 October 2008 (2008-10-11) (v2.6.27)	2–3 years	Varies	Linux kernel v2.6.16 and v2.6.27, were unofficially supported in LTS fashion before a 2011 working group in the Linux Foundation started a formal Long Term Support Initiative.
TYPO3	CMS	January 2011 (2011-01) (v4.5 LTS)	3 years (min.)	Varies	TYPO3 is a web application stewarded by the TYPO3 Association.
Mozilla Firefox	Web browser	31 January 2012 (2012-01-31) (v10.0)	1 year	6 weeks	Mozilla's LTS term is "Extended Support Release" (ESR) (see Firefox#Extended Support Release).
Django	Application framework	23 March 2012 (2012-03-23) (v1.4)	3 years	16 months
Laravel	Application framework	9 June 2015 (2015-06-09) (v5.1)	3 years	1 year	For LTS releases, bug fixes are provided for 2 years and security fixes are provided for 3 years. For general releases, bug fixes are provided for 6 months and security fixes are provided for 1 year.
Windows 10	Operating System	29 July 2015 (2015-07-29) (v10.0.10240)	10 years	4-8 Months	Referred to as "Long Term Servicing Branch", or LTSB, these releases of Windows 10 are supported for 10 years for mission critical machines. The LTSB release gets monthly security updates; the updates to the LTSB release bring little to no feature changes. The LTSB release is available only for businesses running the Windows 10 Enterprise Edition. Regular consumers on the Current Branch (CB) get new versions of the operating system approximately every four months while business customers on the Current Branch for Business (CBB) get upgraded to new versions about every eight months. For more information, please see Windows 10 version history.
Node.js	Runtime system	12 October 2015 (2015-10-12) (v4.2.0)	18 months	12 months

1.^ The support period for Ubuntu's parent distribution, Debian, is one year after the release of the next stable version. For Debian 6.0 "Squeeze" there is an LTS project to provide security updates until February 2016. Decision on providing LTS for later releases is pending.

See also

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