I'm trying to install a custom 18.04 ISO on a Dell Optiplex 9020 via USB stick, and get "No installable kernel was found in the defined APT sources."
When I install using the same ISO on VirtualBox, I don't see this error.
For both machines, I see /cdrom/pool/main/l/linux-signed/linux-image-4.15.0-20-generic_4.15.0-20.21_amd64.deb, and that package is listed in /cdrom/dists/bionic/main/binary-amd64/Packages.gz. For both machines, /target/etc/apt/sources.list is just:
deb cdrom:[Ubuntu-Server 18.04 LTS _Bionic Beaver_ - Release amd64 (20180426)]/ bionic extras main restricted
But when I run from the installer console:
chroot /target apt-cache search linux-image
On the 9020 this returns nothing, but in VirtualBox I see packages listed. Also, when I run
chroot /target apt-cache policy
In the VM, it shows 2 directories each for main and restricted (amd64 and i386), and 1 for extras amd64. On the 9020, it only shows the extras directory.
Why would that be? Is there some information the installer doesn't get when running on the 9020?
chroot /target apt update
Ign:1 cdrom://Ubuntu-Server 18.04 LTS _Bionic Beaver_ - Release amd64 (20180426) bionic InRelease Ign:1 cdrom://Ubuntu-Server 18.04 LTS _Bionic Beaver_ - Release amd64 (20180426) bionic Release Reading package lists... Done Building dependency tree Reading state information... Done
But 'apt-cache policy' still returns the same result as before.
Running 'chroot /target apt --print-uris update' finds all the paths, but the files listed are Packages.xz, not Packages.gz, the size is 0, and there's no hash! The lines are like:
'cdrom://[Ubuntu-Server 18.04 LTS _Bionic Beaver_ - Release amd64 (20180426)]/dists/bionic/main/binary-amd64/Packages.xz' Ubuntu-Server%2018.04%20LTS%20%5fBionic%20Beaver%5f%20-%20Release%20amd64%20(20180426)_dists_bionic_main_binary-amd64_Packages 0
EDIT: I tried this on another VirtualBox VM and saw the same error. So the one good VM is 'dirty' somehow! The same symptoms all apply, though.
After some more examination, the problem was that not all apt-ftparchive commands were getting run. See below. If someone explains to me how one VBox could find the Packages and another couldn't, I will mark that as the answer.