On Wed, Jan 24, 2018 at 04:51:35PM +0000, Michael Fothergill wrote: > root@mikef-PC:/etc/apt# apt-get -t experimental install > linux-headers-4.15.0-rc8-all-amd64 > Reading package lists... Done > > and got the following error: > > > E: The value 'experimental' is invalid for APT::Default-Release as such a > release is not available in the sources Just get the package(s) directly from http://packages.debian.org/experimental/