To followup to what Kees said, to deal with packages that don't include a buildtime generated debsums md5sum file, by default the debsums package also installs an apt hook to generate a debsums as part of the package installation process. Thus, one way to generate the debsums file for those packages that are missing them is to apt-get install --reinstall them.
The package "debsums" is what you want to install to perform hash checks against installed packages.
For example, to check for changed files:
Note that not all packages ship with md5sum file lists. You can see a list of those on your system with:
To followup to what Kees said, to deal with packages that don't include a buildtime generated debsums md5sum file, by default the debsums package also installs an apt hook to generate a debsums as part of the package installation process. Thus, one way to generate the debsums file for those packages that are missing them is to apt-get install --reinstall them.