Public bug reported:
Because EFI does not support instantaneous read of modifier keys (i.e.
holding down shift at boot), the only way to reliably show a boot menu
is by letting the system boot, interrupting the boot, and letting the
menu be displayed because 'recordfail' has been set.
If /boot/grub is on LVM, recordfail does not work, because grub doesn't
have write support on LVM, so saveenv doesn't work. Indeed, from the
grub.cfg on such a system, the recordfail function is written as:
function recordfail {
set recordfail=1
# GRUB lacks write support for lvm, so recordfail support is disabled.
}
The interaction of these two limitations means that systems with
/boot/grub on LVM cannot reliably get a grub menu, ever.
While I think that in the long term we should always put /boot/grub on
the ESP (which means it will always be writable by grub), which is in
fact what we did for Ubuntu Core, in the meantime I believe what we need
to do here is always show the boot menu if we are booted under EFI and
we have a non-writable grubenv.
** Affects: grub2 (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1800722
Title:
EFI booting + /boot on LVM == inaccessible boot menu
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