Something on our company's network is causing some apt updates to fail during an unattended install. We recently discovered that we can fix the apt problem on a previously successful installation using the following options:
sudo apt-get update -o Acquire::http::No-Cache=true -o Acquire::http::Pipeline-Depth=0
Or by putting these options in /etc/apt/apt.conf.d/80http
Acquire::http::No-Cache true; Acquire::http::Pipeline-Depth 0;
However, I still don't know how to modify a preseed.cfg file so that it will use these options for apt. Thanks in advance for your help.