How to manually boot Arch Linux from preboot emergency shell?

Question

I broke an Arch Linux installation. Let's say I made a typo in the PARTUUID string. The result is that the boot process can't mount the root file system and stops at the mkinitcpio preboot stage with the error message:

Your are now being dropped into an emergency shell.

Regression #1: mount + exec

blog.entwicklerseite.de has an example how to manually boot from rootfs, like:

# mount /dev/sda2 /new_root/
# exec /usr/bin/switch_root /new_root /sbin/init

That brings these messages to the console output:

Trying to run as user instance, but the system has not been booted with systemd. 
Trying to continue (this will most likely fail) ... 
...
ERROR: Failed to mount the real root device. 
Bailing out, you are now on your own. Good luck.
... 

And a kernel panic.

Regression #2: set root + mount + exec

# root=/dev/sda2
# mount /dev/sda2 /new_root/
# exec /usr/bin/switch_root /new_root /sbin/init

No change in the output with that version.

With which commands can I continue booting (manually) from the Arch Linux emergency shell?

Answer 1

Later I found a posting on the Arch Linux forum, in thread "Arch fails to mount my root partition".

The solution to boot Arch Linux from the emergency shell is even less typing:

# mount /dev/sda2 new_root
# exit