[arch-general] How to cache pacman mirror for LAN

[Takayuki Muranushi]

Hello,

I'm building a computer cluster with about 20 nodes, all of them
running ArchLinux. One of them is the 'login' node connected to the
Internet, other nodes share Internet connection via the login node
being a router.
https://wiki.archlinux.org/index.php/Internet_Share

Now, when I update the system (pacman -Syu) or install package on all
node, I think it's a bad idea because it will consume the mirror
bandwidth proportional to the number of the nodes. Maybe it's not a
big issue for 20 nodes, but I'd like to learn nevertheless for future
use, that:

Is there a way to cache the pacman transaction at the login node, so
that the communication between the login node and the mirror is
constant, and the rest of communications only take place within the
LAN?
Is seting up a pacman mirror at the login node is the correct solution?

Best,

Takayuki Muranushi