Older dotnet core version supported on Server

Question

I am interested in knowing what dotnet core End of support means for certain versions.

1) Does it mean old .net core libraries installed on servers needs to be removed?
2) Is it done by MS patch updates or we have to remove them?
3) Can old libraries remain on the servers without security vulnerabilities
4) Is App build/test and redeploy needed to have them run on patched versions of libraries? E.g. 3.1.1 to 3.1.27 or 6.0.1 to 6.0.7
5) Is App build/test and redeploy needed to make them run on new major versions e.g. 3.x to 6.x of .net core

Answer 1

1) Does it mean old .net core libraries installed on servers needs to be removed?

best security practices say yes.

2) Is it done by MS patch updates or we have to remove them?

you need to remove

3) Can old libraries remain on the servers without security vulnerabilities

not a best practice.

4) Is App build/test and redeploy needed to have them run on patched versions of libraries? E.g. 3.1.1 to 3.1.27 or 6.0.1 to 6.0.7

depends. if self contained release, a build and redeploy is required. if using shared installed libraries no.

5) Is App build/test and redeploy needed to make them run on new major versions e.g. 3.x to 6.x of .net core

yes. you also need to update the version in the project

Answer 2

According to the documentations, "End of support" refers to the date after which Microsoft no longer provides fixes, updates, or technical assistance for a product version.

Here are answer to your questions:

1. It's recommended to not use those .NET versions which their support has ended, and it's recommended to uninstall them.
2. You need to uninstall them yourself.
3. Since Microsoft will no longer provide fixes or updates for those .NET versions which their support has ended, then by using those versions you may put your data/servers at risk.
4. Patches (service updates) are expected to maintain compatibility; so usually a build/test is not necessary.
5. Major release are not expected to maintain compatibility; so while your application may run if you set up roll-forward rules, but at run-time it may encounter issues because of the breaking changes. So in addition to build/test, you may even need to follow some upgrade instructions.

To learn more you can take a look at the following articles:

• .NET and .NET Core Support Policy
• Releases and support for .NET (.NET 5+ and .NET Core)
• Overview of how .NET is versioned
• Select the .NET version to use
• Running .NET Core Apps on a Framework other than Compiled Version? - Rick Strahl
• Exploring the new rollForward and allowPrerelease settings - Andrew Lock