How to clean up full /boot safely?

[Colin Watson]

On Mon, Feb 12, 2018 at 01:26:20PM +0100, Liam Proven wrote:
> On 12 February 2018 at 11:53, Colin Watson <cjwatson at ubuntu.com> wrote:
> > All your examples are supported by GRUB.
> >
> > Of course it's necessary for GRUB to track on-disk format changes, and
> > the more code you're relying on in the boot loader the more there is to
> > go wrong, so it's true that there "might" be problems
> 
> > Things like
> > LVM are pretty safe these days
> 
> "Pretty"

OK, at this point (and in most of the rest of it) you're just having a
go at my idiolect.  I tend to stick qualifiers on things out of habit,
and I don't always remember to remove them in a later editing pass.  It
doesn't have much bearing on my actual level of confidence in something.
Sorry about that; I'm a developer, not a technical writer.

One thing I particularly enjoy about developing GRUB (specifically GRUB
2 rather than 0.9x - the latter has some similar ideas but in a much
more primitive form) is that the block device and filesystem access code
is written such that the same code works in userspace as well as in the
boot loader, and it's used by grub-install.  This allows for a high
degree of confidence: if grub-install works, then you know that GRUB
understands the block device and filesystem layout.  And if something
goes wrong, because it's software and it would be naïve to pretend that
it never will, then it can be debugged using grub-fstest using normal
Unix tools rather than the limited environment available at boot time.

> I'm a pretty old hand now.

It's obviously fine to be technically-conservative.  But you made a very
specific claim which went above and beyond merely not wanting to use
more complex facilities:

  "the kernel must be on something GRUB can read, i.e. a straightforward
  Linux filesystem."

I called you on that claim, because it's incorrect; GRUB can read more
than just straightforward Linux filesystems, and has been able to do so
in one form or another for well over a decade.  If you meant "e.g."
rather than "i.e.", then that would be different.

-- 
Colin Watson                                       [cjwatson at ubuntu.com]