first draft of README

README.rst

@@ -98,10 +98,9 @@ Package sets and toolchains
 MPSD software releases
 ~~~~~~~~~~~~~~~~~~~~~~
 
-As ``explained in the MPSD HPC documentation
-<https://computational-science.mpsd.mpg.de/docs/mpsd-hpc.html#software>``__, we
+As ``explained in the MPSD HPC documentation <https://computational-science.mpsd.mpg.de/docs/mpsd-hpc.html#software>``__, we
 label software releases available on the HPC using a naming scheme of the year
-(such as `23``) and a letter starting from ``a``. There is an exception that
+(such as ``23``) and a letter starting from ``a``. There is an exception that
 the first available software version is ``dev-23a`` (starting with ``dev-`` to
 indicate this was a development prototype).
 
@@ -112,7 +111,7 @@ For each MPSD software release, multiple toolchains and package sets are availab
     $> ./mpsd-software.py available dev-23a
 
     MPSD software release dev-23a, AVAILABLE for installation are
-    Toolchains: 
+    Toolchains:
         foss2021a-cuda-mpi
         foss2021a-mpi
         foss2021a-serial
@@ -129,11 +128,40 @@ Prerequisites
 
 What needs to be installed for the installation to succeed?
 
+1. ``mpsd-software.py`` installation requirements
++++++++++++++++++++++++++++++++++++++++++++++++++
+
+- a recent version of Python3 (3.9 or newer)
+
+- an environment variable MPSD_MICROARCH to point to the correct microarchitecture of the computer
+- or the ``archspec`` command in the search path that can determine this.
+  Install ``archspec`` as ``pip install archspec`` or ``pipx install archspec``.
+  If you are on a MPSD-maintained linux laptop, you can probably also use
+  `apt-get install archspec`.
+- Optional: if the ``rich`` package is available, some output will be coloured. (Debian package: `python3-rich` or `pip install rich`)
+
+2. Spack requirements
++++++++++++++++++++++
+
+To be able to compile the toolchains, one needs standard build tools (required by spack). On Debian/Ubuntu, this includes the packages:
+
+autoconf
+automake
+build-essential
+ca-certificates
+coreutils
+curl
+file
+gfortran
+git
+libtool
+lmod
+openssh-server
+python3
+rsync
+unzip
+wget
+
 Probably an ongoing topic of work. We know the following tools need to be available:
 
 - XXX TODO, add, requirements in container from CI might be best. Things like rsync, git, buildtools, Linux-headers,
-
-
-
-
-