installed Arch Linux but cannot boot

Boot from your bootable USB Arch-linux , mount all your partitions and chroot into the system.

As montioned jasonwryan :

You need to mount your ESP to /boot

First create the efi folder:

mkdir /boot/efi

mount the esp partition

mount /dev/sda1 /boot/efi

Verify your /etc/fstab , the esp mount point need to be added to fstab.

Create a new sub-directory /boot/efi/EFI/arch/

mkdir -p /boot/efi/EFI/arch/

Move /boot/vmlinuz-linux , initramfs-linux.img and initramfs-linux-fallback.img :

cp /boot/vmlinuz-linux /boot/efi/EFI/arch/vmlinuz-linux.efi
cp /boot/initramfs-linux.img /boot/initramfs-linux-fallback.img /boot/efi/EFI/arch

Run mkinitcpio -p linux then update GRUB:

grub-mkconfig -o /boot/grub/grub.cfg

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