kernel-signed-image-4.4.0-21-g software package provides Signed kernel image generic for the Debian installer, you can install in your Ubuntu 16.04 LTS (Xenial Xerus) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install kernel-signed-image-4.4.0-21-g
kernel-signed-image-4.4.0-21-g is installed in your system.
Make ensure the kernel-signed-image-4.4.0-21-g package were installed using the commands given below,
$ sudo dpkg-query -l | grep kernel-signed-image-4.4.0-21-g*
You will get with kernel-signed-image-4.4.0-21-g package name, version, architecture and description in a table
| Distro | Ubuntu 16 04 lts xenial xerus |
| Section | debian-installer udeb packages |
| Package | kernel-signed-image-4.4.0-21-g |
| Version | 4.4.0-21.37 |
| Description | Signed kernel image generic for the Debian installer |
| Sub Section | Debian-installer |