How to copy Mac OS from a neighboring MacBook?

Question

macOS

There is one poppy beech with the departed OS. You need to install a new OS there. You can’t take it from the Internet, because there are problems with traffic. But fortunately there is a zero MacBook, and the question arose. How to copy the OS to the first Macbook?
First: MacBook 13 pro retina 128gb
Second: MacBook 13 pro retina 500gb

Answer 1

If the OS has flown away, it doesn’t matter, there is a recovery mode on poppies, reboot with Command-R held down or just with Option held down, and then select boot from partition recovery. If this does not help, then on the live computer we go to System Settings - Boot Volume, there will be an "External Disk Mode" button below, we take a thunderbolt cable, connect both poppies with it, on a dead computer we hold Option again when booting, but we take the image as an image for recovery from a live poppy. There is another option, on a live poppy, create a bootable USB flash drive using disk utility, then boot from this flash drive.

Answer 2

@RicoX if in fact, then I accidentally deleted the OS partition. I wanted to return everything to the factory settings :( command + R asks for a wifi connection. But my traffic does not allow downloading. I wonder how much what it tries to download weighs.