Bug#783859: grub-pc: wheezy->jessie: should make sure new core.img fits before removing old module files

[Samuel Bronson]

Package: grub-pc Version: 2.02~beta2-22 Severity: important

When I upgraded this system to from wheezy to jessie, I got a 
dialog box something like this:

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????????????????????????????????? Configuring grub-pc ??????????????????????????????????
?                                                                                      ?
? GRUB failed to install to the following devices:                                     ?
?                                                                                      ?
? /dev/sda                                                                             ?
?                                                                                      ?
? Do you want to continue anyway? If you do, your computer may not start up properly.  ?
?                                                                                      ?
? Writing GRUB to boot device failed - continue?                                       ?
?                                                                                      ?
?                        <Yes>                           <No>                          ?
?                                                                                      ?
????????????????????????????????????????????????????????????????????????????????????????
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This was kind of frustrating, especially in view of the fact that 
it seemed to be concealing the actual output of grub-install.  (It 
was.)

So I decided to investigate this later, when I could do the install in a
way that would permit me to actually see the output.  Unfortunately, I
forgot, so my system ended up with an old core.img that couldn't find
the new modules, and didn't expose all the symbols they needed anyway.

But I've fixed it now, and this is what grub-install had to say:

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(At the time, my first partition began at sector 63.  I've since shrunk
it to start at 1MiB.)

Here are my core.img files:
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Name: core.img
Type: application/octet-stream
Size: 28839 bytes
Desc: Wheezy core.img
URL: <http://lists.alioth.debian.org/pipermail/pkg-grub-devel/attachments/20150430/17d6193c/attachment-0002.obj>
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A non-text attachment was scrubbed...
Name: core.img
Type: application/octet-stream
Size: 32044 bytes
Desc: Jessie core.img
URL: <http://lists.alioth.debian.org/pipermail/pkg-grub-devel/attachments/20150430/17d6193c/attachment-0003.obj>
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I'm not sure why the Jessie one is so much bigger; I've had no 
success in deciphering the contents. 

-- Package-specific info:
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-- System Information: Debian Release: 8.0 
  APT prefers stable-updates APT policy: (500, 'stable-updates'), 
  (500, 'stable') 
Architecture: amd64 (x86_64) Foreign Architectures: i386

Kernel: Linux 3.16.0-4-amd64 (SMP w/2 CPU cores) Locale: 
LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8) Shell: 
/bin/sh linked to /bin/bash Init: sysvinit (via /sbin/init)

Versions of packages grub-pc depends on: ii  debconf [debconf-2.0] 
1.5.56 ii  grub-common            2.02~beta2-22 ii  grub-pc-bin 
2.02~beta2-22 ii  grub2-common           2.02~beta2-22 ii  ucf 
3.0030

grub-pc recommends no packages.

grub-pc suggests no packages.

-- debconf information: * grub-pc/install_devices: 
/dev/disk/by-id/ata-TOSHIBA_MQ01ABF050_24EPTRJFT 
  grub-pc/install_devices_disks_changed: 
* grub-pc/install_devices_failed: true grub2/linux_cmdline: 
  grub-pc/hidden_timeout: false grub-pc/partition_description: 
  grub2/kfreebsd_cmdline_default: quiet 
  grub-pc/chainload_from_menu.lst: true 
  grub2/device_map_regenerated: grub-pc/postrm_purge_boot_grub: 
  false grub-pc/kopt_extracted: false grub2/kfreebsd_cmdline: 
  grub-pc/timeout: 15 grub-pc/mixed_legacy_and_grub2: true 
* grub2/linux_cmdline_default: quiet 
  grub-pc/disk_description: 
  grub-pc/install_devices_failed_upgrade: true 
  grub-pc/install_devices_empty: false 
  grub2/force_efi_extra_removable: false