Comment 39 for bug 1918427

* dann frazier <email address hidden> [2021-03-19 12:16]:
> On Fri, Mar 19, 2021 at 10:01 AM Ryan Harper <email address hidden> wrote:
> >
> > * dann frazier <email address hidden> [2021-03-18 16:30]:
> > > On Thu, Mar 18, 2021 at 12:25 PM Ryan Harper <email address hidden> wrote:
> > > >
> > > > * dann frazier <email address hidden> [2021-03-18 12:11]:
> > > > > On Thu, Mar 18, 2021 at 10:25 AM Ryan Harper <email address hidden> wrote:
> > > > > >
> > > > > > * dann frazier <email address hidden> [2021-03-17 20:30]:
> > > > > > > On Tue, Mar 16, 2021 at 10:05 AM Ryan Harper <email address hidden> wrote:
> > > > > > > >
> > > > > > > > Hi Dan,
> > > > > > > >
> > > > > > >
> > > > > > > 1) flash-kernel could get installed post-divert. In that case,
> > > > > > > flash-kernel's own postinst will cause it to run and then fail. This
> > > > > > > happens today if you start with a cloud image w/o flash-kernel
> > > > > > > pre-baked because Ubuntu's kernel recommends flash-kernel, causing it
> > > > > > > to be installed along with the kernel. Official cloud images happen to
> > > > > >
> > > > > > Hrm, so if we take a squashfs rootfs (with no flash-kernel present)
> > > > > > chroot into it and install the linux-image-generic package pulling in
> > > > > > flash-kernel this fails due to postinst of flash-kernel expecting
> > > > > > initramfs to already be generated? This doesn't seem like a curtin bug.
> > > > >
> > > > > If done so in a chroot that exposes the kernel interfaces (/proc &
> > > > > /sys) that claim to be hardware that requires the initramfs to be
> > > > > post-processed, yes.
> > > >
> > > > Maybe I'm missing something but if I install linux-image-generic
> > > > it populates /boot with vmlinuz-$version (and a few more things)
> > > > and /lib/modules/$version and the kernels postinst will invoke
> > > > update-initramfs. The /boot/initrd.img-$version is *generated* at
> > > > that time during the kernel's postinstall
> > > >
> > > > Now, in the arm case IIUC, the kernel package has a dep on flash-kernel
> > > > being present as it's "needed" to generate the initramfs ... so how can
> > > > flash-kernel's postinst *fail* if it is the tool that's generating said
> > > > initramfs file?
> > >
> > > What flash-kernel does is generate wrapped versions of *exisiting*
> > > vmlinuz and initrd.img files. It doesn't generate those files, rather
> > > post-processes them.
> > > The kernel doesn't depend on flash-kernel, it just recommends it like
> > > it does GRUB on x86.
> >
> > Yes, I get that but it still looks like a packaging bug if dpkg installs
> > flash-kernel first and /boot is not populated with existing initrds; one
> > could easily see this happen in a debootstrap.
>
> Given that a failure to produce a wrapped initrd could cause a system
> to become unbootable, it does seem to me like a hard failure here is
> warranted. But, perhaps we could provide a "shhhh... it's ok, just
> chill" mechanism. Maybe a FLASH_KERNEL_SKIP=1 environment variable?

Agreed but with the condition that the *input* is present. If the
initrd file has not yet been generated then another error from
flash-kernel seems redundant, specifically in the case where if the
kernel package is not yet installed (and maybe this is the reasonble
check the post-inst can do) then it's *always* going to fail.

Does flash-kernel hook into initramfs updates via the
/etc/kernel/{pre,post}inst.d/flash-kernel ? like initramfs-tools does?

I suspect most of what flash-kernel does would be triggered via kernel
postinst hooks.

>
> > Is the "liveness" of the chroot what's tripping up flash-kernel? We
> > currently run inside a chroot which mounts /dev /proc /run and /sys; we
> > could drop those but it also seems reasonable to have flash-kernel not
> > expect existing initrds?
>
> Certainly a non-live chroot can avoid this by leading f-k to believe
> it does not recognize the system. In fact, ISTR bind mounting certain
> files in build chroots to trick f-k into doing nothing.

Interesting. That may be another approach; though that would be a f-k
specific mount for curtin to swallow when installing one package; we
might not know it's getting installed (like as a Recommends with the
linux-image-generic) so that might not be as useful.