initramfs update error

Duringa ubuntu linux system update an initramfs error sometimes come up:

update-initramfs: Generating /boot/initrd.img-x.x.x.x-generic

.: 4: Can't open /scripts/functions

Often this results in broken update, and many other issues.
If the system is unable to boot to the new updated kernel, select the older version from the boot menu and try updating initramfs again.

Then try the following:

1, Delete only broken files in /var/lib/initramfs-tools/. (Be careful, delete onlt if you are sure of what you are doing, else you may try the other steps skipping this.)
2, sudo dpkg --configure -a
3, sudo dpkg --configure initramfs-tools (make sure no errors, otherwise repeat step 1 & 2).
4, sudo update-initramfs -u (Maybe not neccessary).