Re: problem installing grub to linux mint partition

[Pascal Hambourg]

Le 03/06/2018 à 15:11, David H. Durgee a écrit :
> > Le 03/06/2018 à 02:24, David H. Durgee a écrit :
> >
> >     I am encountering problems attempting to install grub on a linux 
> > mint 18.3 (sylvia) partition on a multi-boot system.  When booting the 
> > live DVD and invoking its installer the partition is not listed as a 
> > target to install grub.
> >
> > Which devices are listed ?
>
> The only partitions listed as possible grub targets were the master boot 
> record, a FreeDOS partition and two NTFS formatted Windows partitions. 
> The JFS formatted linux and eCS partitions, including the target for the 
> new installation, were not listed as possible grub targets.

Could the first three partitions be primary partitions and the other 
ones be logical partitions ? Then the Mint installer may consider that 
there is no point in installing GRUB in a logical partition PBR, as it 
cannot be booted from a standard MBR (however it can still be 
chainloaded from another boot loader).

> You are correct, I ran grub-install and grub-probe in a terminal window 
> started from the Live DVD session.  I have NOT installed sylvia yet, so 
> chrooting is not an option at this point.  Given I cannot select the 
> proper target for the grub install I aborted the install itself.

Do you mean that the Mint installer offers to install GRUB before 
installing the base system ? Weird.

> I had not thought that grub-probe error related to the source instead of 
> the target.

The error is not related to the source. The /boot directory is a target too.

The GRUB for BIOS boot loader installed by grub-install is divided in 
three parts :
1 - the boot image is installed in a disk (MBR) or a partition (PBR) 
boot sector
2 - the core image is installed on the same drive as the boot record ; 
the exact location can vary and is selected automatically by 
grub-install, you do not have direct control over it
3 - modules, config files, fonts, language files... are installed in the 
/boot/grub directory or ${boot-directory}/grub if specified ; it can be 
on a different drive.

grub-install must be able to map these locations to "real" drives, 
because they must be readable using disk BIOS calls (int13h) at boot 
time. You get the error because the current /boot is included in a AUFS 
filesystem which cannot be mapped to a real drive. Anyway, this would be 
the wrong location. You want /boot in /dev/sda15, not in the installer's 
virtual root filesystem.

> Can you confirm for me that JFS is a supported grub install target?

No, because I do not use JFS. But I wonder why GRUB would drop support 
for JFS and I can see that the current development GRUB packages in 
Debian still include the jfs module.

<https://packages.debian.org/sid/amd64/grub-pc-bin/filelist>

> I can see from the targets listed that FAT and NTFS are supported, but 
> obviously I am not going to install linux on either of those.

Note that installing GRUB's boot image on a given target device does not 
require that GRUB fully supports its filesystem. The only requirement is 
that GRUB know that the boot sector format leaves enough available space 
to install the boot image. GRUB must only support the filesystem 
containing /boot, because this is where GRUB files and kernel files are 
located.