Which a) FLOSS b) stable (= not rolling release) c) desktop GNU/Linux distributions have a long security update support?
Of course it’s interesting which distro has the longest support, but 2nd, 3rd etc. places should be considered, too.
Debian stable versions get security updates for around 1 year after the new stable version is released. In theory this could be a long time, but you can’t know for sure, can you?
Ubuntu LTS versions get security updates for 5 years.
Any distro offers more?
NOTE: The terminology you're looking for is EOL aka. End of Life. If you search for this and the name of the distro you'll find most of them in this manner.
CentOS is probably the longest you'll find. From the FAQ:
excerpt: 8. How long will CentOS 5 be supported?
We intend to support CentOS 5 until Mar 31st, 2017 The current plan is this:
- Full Updates (including hardware updates): Currently to Q4, 2012
- Updates ( including minor hardware updates): Up to Q1 of 2014
Maintenance Updates Q1, 2011 - Mar 31st, 2017
Full Updates
During the Full Updates phase, new hardware support will be provided at the discretion of CentOS via Update Sets. Additionally, all available and qualified errata will be provided via Update Sets (or individually {and immediately} for Security level errata.) Update Sets normally will be released 2-4 times per year, with new ISOs released as part of each Update Set. In the 5.x numbering scheme, the .x is the number of the Update Set.
Maintenance Updates
During the Maintenance updates phase, only Security errata and select mission critical bug fixes will be released. There will be few, if any, Update Sets released.
Most of the RHEL/CentOS releases are supported for ~10 years.
excerpt from CentOS EOL - End of Life page
CentOS 5
- 7 years primary support life; later extended to ten years
- Mar 31, 2017 EOL
- i386 x86_64 support
CentOS 6
- 7 years primary support life; later extended to ten years
- November 30, 2020 EOL
- i386 x86_64 support
