install_packages: check for debian

[Maximilian Stein]

Hi there,

to decide if it is running on a Debian system, install_packages(8) 
switched to checking for existence of 
$FAI_ROOT/var/cache/apt/pkgcache.bin a while ago [1].

Unfortunately, this does not always work in my tests with Bookworm, as 
the file seems to be deleted and recreated during an apt update. 
Therefore, install_packages does not check anymore if a package exists 
and simply gives all packages to apt which then fails ("E: Unable to 
locate package lilo"). Before, I only got a warning from 
install_packages itself ("WARNING: These unknown packages are removed 
from the installation list: lilo-").

Do you know a way to work around this (besides removing all non-existent 
packages from package_config/)?

 From my point of view, I think that install_packages probably should 
only check if apt-cache exists and is executable since this is the 
command it needs to execute.

Best,
Maximilian


[1]: 
https://github.com/faiproject/fai/commit/d11fae14fa2f59d2bb93352d54c2b54c4c4f8f93