The problem usually arises when interrupting full upgrade process due to electric interruption, turning off pc before upgrade was complete etc.
The system is unable to boot again with a similar message below:
"Warning: /lib/modules/4.14.15-1-ARCH/modules.devname not found - ignoring. starting version 236.
ERROR: resume: hibernation device 'UUID… not found.
ERROR: device 'UUID…not found skipping fsck."
The error is related with initramfs.
To fix it the user needs to boot a livecd (use Antergos iso, it's easier)
You need to know which device is the right one check with sudo fdisk -l
(/dev/sdXn should be replaced with the right device information)
mount /dev/sdXn /mnt >> / root partition
mount /dev/sdXn /mnt/boot >>> /boot partition
Now upgrade your system
sudo pacman -Syu
And finally fix initramfs (please notice the command bellow uses capital P)
sudo mkinitcpio -P
unmount partitions and reboot your machine