Today I Learnt

Build a system that can install GRUB2 on UEFI and on legacy systems

grub-efi-amd64 and grub-pc are not coinstallable. It turns out however that they do not contain GRUB, but the machinery to keep GRUB configuration up to date on the current system. If I want to be able to install GRUB on other systems, I can use the -bin packages:

apt install grub-common grub2-common grub-efi-amd64-bin grub-pc-bin

That gave me a grub-install command that worked on both kinds of systems.

GRUB configuration on a UEFI system

An old GRUB configuration on a UEFI system gave me this:

error: no suitable mode found
Booting blind

which boots on a blank screen until the kernel reinitialises the video hardware.

The Arch Linux Wiki has excellent documentation for this case, and here's the resulting UEFI GRUB snippet:

insmod efi_gop
insmod efi_uga
insmod font
if loadfont ${prefix}/fonts/unicode.pf2
    insmod gfxterm
    set gfxmode=auto
    set gfxpayload=keep
    terminal_output gfxterm

# Follow with the usual GRUB menu entries…

Use an unsigned local APT repository for testing/development purposes

I found out today that one can have options in square brackets in sources.list:

# In /etc/apt/sources.list.d/local-devel.list
deb [trusted=yes] http://localhost:1234/debian jessie main

pabs on IRC also mentioned local-apt-repository but I haven't tried it.

Booting Jessie Debian Live with a kernel from jessie-backports

This requires working around #844749 and 844749.

In hooks/9000-fix-bugs.chroot I ended up having this:

# Workaround per
if ! grep -q ^nls_ascii /etc/initramfs-tools/modules
        echo "nls_ascii" >> /etc/initramfs-tools/modules

# Workaround per
if ! grep -q ^overlay /etc/initramfs-tools/modules
        echo "overlay" >> /etc/initramfs-tools/modules

Using a custom kernel in Jessie Debian Live

How do I have live-build pick a custom kernel package instead of the default one?

  1. lb config --linux-packages linux-image-$SOMETHING
  2. Use equivs to build a linux-image-$SOMETHING-$ARCH package that depends on the kernel that you built.