This is not a real repo.
All commands should be ran as root since apt-cacher-ng files reside in /var/cache/ which can only be managed by root.
Login to a PC with an up-to-date apt-cacher-ng.
Copy all the contents to your USB drive.
On a PC that needs updating:
apt-get install apt-cacher-ng
if apt-cacher-ng is not installed there.
Then plug in your USB drive and do the following:
cd /var/cache/apt-cacher-ng/ mkdir _import cp /media/YOUR_USB_DRIVE/apt-cacher-ng/* /var/cache/apt-cacher-ng/_import/ chown -R apt-cacher-ng.apt-cacher-ng _import
Now go to 127.0.0.1:3142 in your browser (or use another IP that points to the machine you just copied cacher contents to) and go to "Configuration" page. There, click Import and wait till it's done. Now you have an up-to-date cacher on this PC and updates can be installed quick.