Two weeks ago, when I decided to upgrade my wonderful OS (5.4Gb) as it is usual when you didn't do it for two long months. I was scary but I went ahead. Everything seemed okay, but as long as I restarted my laptop, just second after restarting an ERROR on GRUB boot showed up with a "Minimal Bash console".
What I did as soon as this came out was taking my old laptop and starting to look up on google about the issue. After a lot of goes I found the key. To sum up, we have to restart our ArchLinux by grub commands. Following steps describe how I got it:
Step1: Choose the OS kernel and which partition is stored (remember tab key shows you suggestions)
$ kernel /vmlinuz##PUSH TAB## root=/dev/sdaX ro
Step2: Launch linux image file:
$initrd /initranfs##PUSH TAB##.img quiet spash
Step3: Boot (good luck!!! xD)
In case you hit the right partition for your OS, this should be running correctly and then the last step left is going to be reinstall your grub package.
In case you didn't get you OS running, another mode is set up. On this mode you are able to make some probes which will help you to find out why your OS didn't run. On this new console mode you can mount partitions using the command "mount", and within dev folder you have every partitions are installed on your machine, then only mount one by one until you find the correct one, restart your computer, probe again above steps(1,2,3) and good luck ;)