Grub 2 Error: Invalid Signature press any key to continue…

Grub 2 Error Booting Windows:

Error: Invalid Signature
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Solution
Step-1: Find UUID by running the command:

$ sudo blkid

/dev/sda1: UUID="6b37e778-0fd6-470f-b65b-4f922e720b42" TYPE="ext4"
/dev/sda5: UUID="7a721379-43f5-4752-9a46-f0f9f3fa14e3" TYPE="swap"
/dev/sda6: UUID="73f63f9c-bfe2-4d85-a7fb-557a19617884" TYPE="ext4"
/dev/sdb1: LABEL="iSHY-EHDD" UUID="687D0AAA333A2C12" TYPE="ntfs"

Step-2: Edit 40_custom grub file:

$ sudo vi /etc/grub/40_custom

#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.

menuentry "Windows 8" {
insmod ntfs
set root=(hd0,1)
search --no-floppy --fs-uuid --set 687D0AAA333A2C12
chainloader +1
}

It would boot from the /dev/sdb1 drive.
Step-3: It will add the new entry in the grub.

$ sudo grub-mkconfig
$ sudo update-grub2