Add documentation on EESSI versions

docs/repositories/versions.md

@@ -0,0 +1,22 @@
+# EESSI Versions
+
+EESSI is organized in different dated versions. Each EESSI version contains a version of the [compatibility layer](../compatibility_layer.md) and its' own set of software applications. In addition, a particular EESSI version will target a different set of [common toolchains](https://docs.easybuild.io/common-toolchains/) to build software with. As an example, the first  EESSI version was released in June 2023 and is named `2023.06`. This version's compatibility layer is based on a particular "version[^1]" of [Gentoo Prefix](https://wiki.gentoo.org/wiki/Project:Prefix) and the software layer contains software built using the `foss/2022b`, `foss/2023a`, and `foss/2023b` [software toolchains](https://docs.easybuild.io/common-toolchains/#common_toolchains_overview) as defined in EasyBuild.
+
+The vast majority of changes are fully transparent to users. Apart from selecting a newer version when starting up EESSI, and accessing an update collection of software, the functionality remains the same, with little to no extra effort needed to use a new version compared to and older one.
+
+Going forward, EESSI aims to have yearly version releases, which will target a more recent set of toolchains and an updated set of compatibility layer components.
+
+## Current EESSI versions
+
+| EESSI Version       | Included toolchains                    | Software list                                                     |
+| ------------------- | -------------------------------------- | ----------------------------------------------------------------- |
+| 2023.06 (default)   | `foss/2022b` `foss/2023a` `foss/2023b` | [2023.06](https://www.eessi.io/docs/available_software/overview/) |
+| 2025.06             | `foss/2024a` `foss/2025a`              | Coming Soon                                                       |
+
+The current default EESSI version is `2023.06`. Version `2025.06` is already fully available and will be made the default soon, once it contains more software. 
+
+## Switching between EESSI versions
+
+* The simplest way to load a specific EESSI version or to switch between them, is to load the appropriate environment module. To access version `2023.06` one can simply do `module load EESSI/2023.06` and switching to the `2025.06` version is just as easy with: `module load EESSI/2025.06`. This will automatically set up the environment and avoid conflicts between versions.
+
+[^1]: technically: a specific commit, since Gentoo Prefix doesn't have versioned releases.

docs/systems.md

@@ -57,6 +57,7 @@ EESSI is supported in the ARM and GPU-accelerated partitions of Deucalion with p
 MareNostrum 5 is the EuroHPC JU supercomputer hosted by the [Barcelona Supercomputing Center (BSC)](https://www.bsc.es/).
 
 * [General documentation](https://www.bsc.es/supportkc/)
+* [EESSI @ MareNostrum 5](https://www.bsc.es/supportkc/docs/MareNostrum5/Package%20Managers/EESSI)
 
 ---
 
@@ -68,6 +69,7 @@ MareNostrum 5 is the EuroHPC JU supercomputer hosted by the [Barcelona Supercomp
 
 * VSC-5: [General documentation](https://docs.asc.ac.at/systems/vsc5.html) | [EESSI @ VSC-5](https://docs.asc.ac.at/software/eessi.html)
 * MUSICA: [General documentation](https://docs.asc.ac.at/systems/musica.html) | [EESSI @ MUSICA](https://docs.asc.ac.at/software/eessi.html)
+
 MUSICA is currently in a closed test phase, with open testing to follow. It is expected to be operational by the end of 2025.
 
 ### Belgium

mkdocs.yml

@@ -26,7 +26,9 @@ nav:
   - Available software and repositories:
       - Software: available_software/overview.md
       - Repositories:
-        - Production: repositories/software.eessi.io.md
+        - Production:
+          - Software: repositories/software.eessi.io.md
+          - Versions: repositories/versions.md
         - RISC-V: repositories/riscv.eessi.io.md
         - Development repository: repositories/dev.eessi.io.md
   - Installation and configuration:
@@ -142,6 +144,8 @@ markdown_extensions:
   - admonition
   # support for using MarkDown in HTML
   - md_in_html
+  # support for footnotes
+  - footnotes
   # code blocks with syntax highlighting, graphs
   - pymdownx.superfences:
       custom_fences: