[R-pkg-devel] preventing auto-update of R and c2d4u r-cran-* packages on Ubuntu 22.04

In the past, I've extracted the pre-built debian packages into the 
user's personal folder, instead of installing them via apt. It worked 
(but it was not fun), and was pretty manual.? That might interact a bit 
better with some of the third party tools for dealing with dependencies 
in shiny apps, compared to system-wide installs; ymmv.

Thank you for the suggestion. My implemented approach works indeed 
similar to this.

After moving this discussion to R-SIG-Debian 
(https://stat.ethz.ch/pipermail/r-sig-debian/2023-August/thread.html), 
Dirk Eddelbuettel suggested five different approaches.

I made indeed a snapshot (a local copy) of the complete "site-library" 
folder to another place of the file system (e.g. 
"site-library-snapshot"). In the .Renviron file of the shiny user, the 
environment variable R_LIBS_USER then points to this location. The base 
packages from "library" are conservative, so I decided to use them from 
the original position.

Finally, an rmarkdown script provided by the shiny-server can report the 
value of .libPaths() and versions and locations of installed packages:

installed.packages()[,2:3]

This works well, except for a package that contained relative symbolic 
links to the file system.

Thomas