How to remove a record of an installed package without removing the installed files in Linux

If you are working with Raspberry Pi or any other Linux systems and you want to protect how you set up the board, you can use this method to remove the record of custom packages that you have installed. It will make it harder for people to reverse engineer your setup. 

They can still clone your SD card and use it on other RPi boards. For that, you can refer to How to prevent Raspberry Pi SD card cloning blog post.

Open /var/lib/dpkg/status file with a text editor.

Find a block that belongs to the software package you want to remove and it looks something like this:

Package: xserver-xorg-input-vmmouse
Status: install ok installed
Priority: optional
Section: x11
Installed-Size: 136
Maintainer: Ubuntu Developers <ubuntu-devel-discuss@lists.ubuntu.com>
Architecture: amd64
Version: 1:12.7.0-2
Provides: xorg-driver-input
Depends: libc6 (>= 2.7), xorg-input-abi-12, xserver-xorg-core (>= 2:1.10.0-0ubuntu1~), xserver-xorg-input-mouse, udev
Description: X.Org X server -- VMMouse input driver to use with VMWare
 This package provides the driver for the X11 vmmouse input device.
 .
 The VMMouse driver enables support for the special VMMouse protocol
 that is provided by VMware virtual machines to give absolute pointer
 positioning.
 .
 The vmmouse driver is capable of falling back to the standard "mouse"
 driver if a VMware virtual machine is not detected. This allows for
 dual-booting of an operating system from a virtual machine to real hardware
 without having to edit xorg.conf every time.
 .
 More information about X.Org can be found at:
 <URL:http://www.X.org>
 .
 This package is built from the X.org xf86-input-vmmouse driver module.
Original-Maintainer: Debian X Strike Force <debian-x@lists.debian.org>

Remove the whole block and you will remove the installation record of that package. The package will no longer appear to be installed to dpkg; despite all the files still available.