bug#20067: fix interpretation of grub configuration

[Tomáš Čech]

On Sat, Sep 10, 2016 at 12:03:38AM +0200, Ludovic Courtès wrote:
> Good news!

Good news indeed!

> address@hidden (Ludovic Courtès) skribis:
>
> > Tomáš Čech <address@hidden> skribis:
> >
> > > Grub configuration interpretes `linux' as directory where is located
> > > bzImage. If I enter file name instead, result configuration will be
> > > wrong.
> >
> > The solution will be to not automatically append “/bzImage” (and
> > likewise for the initrd.)
> >
> > We could change places where ‘menu-entry’ is instantiated to:
> >
> >   #~(string-append #$kernel "/bzImage")
> >
> > However, there’s the problem that the image name appears in the
> > ‘parameters’ file of the system (as seen in the output of ‘guix system
> > build foo.scm’), where it is unevaluated.  If we use ‘string-append’ as
> > above, a raw (string-append …) sexp will appear in there, which is not
> > nice.
> >
> > To address this, an idea is to add “expanders” for gexps: gexps already
> > have “compilers”, and expanders would be similar except that they would
> > produce something possibly different from just the derivation’s output
> > file name.  For instance, we could write:
> >
> >   (file-append kernel "/bzImage")
> >
> > and that would expand directly to:
> >
> >   "/gnu/store/…/bzImage"
>
> AFAICS this is finally fixed!
>
>  expanders in commit ebdfd776f4504c456d383ee8afa59fc6fdfc6756
>  ‘file-append’ in commit a9e5e92f940381e3a4ee828c6d8ff22a73067e17
>  kernel file name in commit 44d5f54e31039d78f156bd9562dca293124eaa76
>
> Please let me know how it goes!  In particular, does it work for the
> dual-boot scenario you were interested in?

It is almost perfect.

Configuration excerpt...

(bootloader (grub-configuration
             (device "/dev/sda")
             (menu-entries
              (list
               (menu-entry
                (label "openSUSE")
                (linux "(hd0,msdos1)/vmlinuz")
                (linux-arguments (list
                                  "root=/dev/venom/opensuse"
                                  "init=/usr/lib/systemd/systemd"))
                (initrd "(hd0,msdos1)/initrd"))))))


...transforms into

menuentry "openSUSE" {
  search --file --set (hd0,msdos1)/vmlinuz
  linux (hd0,msdos1)/vmlinuz root=/dev/venom/opensuse 
init=/usr/lib/systemd/systemd
  initrd (hd0,msdos1)/initrd
}

I think that if linux contains prefix '(.*)/', there should be no
search for kernel.

Thank you very much for fixing this bug (especially when I wasn't
able). I believe that fixing this bug is big step in more friendly
behavior to other OS.

Best regards,

S_W

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