It first downloads all packages from net, then it proceed totally offline starting by verifying downloaded files, signatures, extracting new packages and finally rebuilding initramfs.
Because arch is replacing the kernel and inittamfs in-place there is a chance that it will not boot if interrupted.
This issue was long resolved on other distro.
One way to mitigate it is by having multiple kernels (like LTS or hardened) that you can always pick in grub if the main one fail.
This issue was solved on Slackware in 1993.
It installs a “huge” kernel that contains all drivers to run on almost any hardware by default, alongside the “generic” kernel with only the modules you need. If the generic kernel fails to boot, you always have the backup, which is known to work, cause it’s the kernel you first boot into after installation.
I’m not familiar with slackware but why is specific kernel called generic, while generic one is not called generic? I’m puzzled
