Is it possible to chainload Windows from illumos boot loader?

Is it possible to chainload Windows from illumos boot loader?

[nsgnkhibdk2cls0f]

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It's very cool if this is possible. OpenIndiana overwrote my MBR so I can no longer boot Windows. I want to dual boot the two systems. I don't want to install third party boot loaders like grub4dos or grub2 (but I can install them if it's required).

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Re: [discuss] Is it possible to chainload Windows from illumos boot loader?

[Toomas Soome]

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> On 30. Jul 2024, at 04:58, nsgnkhibdk2cls0f via illumos-discuss <discuss@lists.illumos.org> wrote:
> 
> It's very cool if this is possible. OpenIndiana overwrote my MBR so I can no longer boot Windows. I want to dual boot the two systems. I don't want to install third party boot loaders like grub4dos or grub2 (but I can install them if it's required).

illumos boot loader has command ‘chain’ for chainloading. In UEFI system, it will take name of efi program as argument, in BIOS system it will take either disk device name with colon at the end (disk0: or disk0p1: etc, see output of lsdev -v), or file name storing 512B copy of MBR or partition boot block — this makes it possible to store original MBR into file, get illumos installed and then set up chainloading.

To configure chainloading with boot loader, there are 2 possible options:

1. set chain_disk variable to have device/file name for chain command. if this variable is set, the extra menu entry is appearing in loader menu screen.

or

2. add entrie(s) into <pool>/boot/menu.lst file, this allows one to specify multiple chain loader setups and they appear in ‘boot environments’ submenu of loader menu.

See also menu.lst(5) and loader(7).

Please note, UEFI chain loading is fragile mechanism in nature (because you are not replacing program in memory but are adding new, so more memory is consumed, memory map will get more fragmented etc), and the results may vary. Afterall, loader is built to load and start this OS and support for chainloading is nice extra feature, but not a primary purpose.

rgds,
toomas


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Re: [discuss] Is it possible to chainload Windows from illumos boot loader?

[nsgnkhibdk2cls0f]

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`chain_disk="disk0s1:"` worked. Thank you.

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