Dual boot alongside W10 on BIOS system: What do i need to do?

---

How exactly do I proceed? Antergos wiki only has a tutorial for UEFI systems.

Before reinstalling Windows I created a 500gb NTFS partition and let another 500gb of unnalocated space to format in ext4 later and install Antergos in it.

Two of the solutions I’ve found when looking around revolved around:

A) Installing GRUB on a separate partition Install GRUB on the same partition as the Distro of choice is installed.

However, When using Cnchi, it does not let me select which partition I want to install GRUB on. It only has one option, which is select the main drive and not specific partitions.

Also, maybe I made some mistake when reinstalling W10, because there’s no boot partition (I think there should be one, afaik and I think there was one before).

My current partition layout is:

/dev/sda1/ >windows partition [ntfs 500gb]

/dev/sda2/ >ext4 partition [ext4 500gb]

Previously I created a 1gb ext4 partition to install grub, but since there wasn’t a way do it with cnchi, I just deleted it and merged it on the rest of the bigger ext4 partition.

@namelessking
Both Windows and Antergos are capable of formatting their partitions during install, so you do not have to preformat them. And both are capable of resizing their partitions after install, too.

Unless there are something more info we should consider, just install Windows first and then Antergos. And you may install grub on the MBR of the same disk.

If your BIOS allows booting from more than one disk, then it is possible to install MBR to e.g. a USB stick. But whether that is reasonable or not depends on what you want to achieve.

Antergos does not need a separate boot partition, and in an ordinary home install I don’t see much need for having a separate boot partition.
But when you say a “boot partition”, do you actually mean an EFI partition?

and as on a bios system grub will be installed inside MBR of the disk, and not onto a partition on a disk there can not be an option to install somewhere else then onto the one and only drive inside your system

@joekamprad
You are right, the only normally sensible way is to install grub into MBR of a disk, otherwise booting is not possible.
However, it is technically possible to install it to a partition, and use it by making a suitable menu entry into e.g. custom.cfg, but it is advanced stuff and seldom anything useful.

@manuel yes but also may the better way to install grub onto dualboot bios system with win10 as second OS, as in my experience win10 updates will do not work in some cases if boot is not owned by window. (millennium updates)

@manuel said in Dual boot alongside W10 on BIOS system: What do i need to do?:

@namelessking
Both Windows and Antergos are capable of formatting their partitions during install, so you do not have to preformat them. And both are capable of resizing their partitions after install, too.

Unless there are something more info we should consider, just install Windows first and then Antergos. And you may install grub on the MBR of the same disk.

If your BIOS allows booting from more than one disk, then it is possible to install MBR to e.g. a USB stick. But whether that is reasonable or not depends on what you want to achieve.

Antergos does not need a separate boot partition, and in an ordinary home install I don’t see much need for having a separate boot partition.
But when you say a “boot partition”, do you actually mean an EFI partition?

In case of a boot partition, I mean a partition just for GRUB.
I don’t want to mess with the MBR because I want to keep the MBR intact so I don’t have issues when updating windows.

@joekamprad said in Dual boot alongside W10 on BIOS system: What do i need to do?:

and as on a bios system grub will be installed inside MBR of the disk, and not onto a partition on a disk there can not be an option to install somewhere else then onto the one and only drive inside your system

So, It’ll overwrite Windows’ bootloader, right?

@manuel said in Dual boot alongside W10 on BIOS system: What do i need to do?:

@joekamprad
You are right, the only normally sensible way is to install grub into MBR of a disk, otherwise booting is not possible.
However, it is technically possible to install it to a partition, and use it by making a suitable menu entry into e.g. custom.cfg, but it is advanced stuff and seldom anything useful.

It’s kinda what I want to do.
I want to set it up like this as it seems the configuration that’ll give me less trouble:

https://askubuntu.com/questions/62440/is-it-possible-to-boot-ubuntu-using-the-windows-bootloader

@joekamprad said in Dual boot alongside W10 on BIOS system: What do i need to do?:

@manuel yes but also may the better way to install grub onto dualboot bios system with win10 as second OS, as in my experience win10 updates will do not work in some cases if boot is not owned by window. (millennium updates)

That’s one reasons I don’t want to overwrite the MBR.

@namelessking BUT arch wiki say:

Warning: GRUB strongly discourages installation to a partition boot sector or a partitionless disk as GRUB Legacy or Syslinux does. This setup is prone to breakage, especially during updates, and is not supported by the Arch developers.

@joekamprad said in Dual boot alongside W10 on BIOS system: What do i need to do?:

@namelessking BUT arch wiki say:

Warning: GRUB strongly discourages installation to a partition boot sector or a partitionless disk as GRUB Legacy or Syslinux does. This setup is prone to breakage, especially during updates, and is not supported by the Arch developers.

I’ve read this.

But I don’t get it. Your previous post was this:

@joekamprad said in Dual boot alongside W10 on BIOS system: What do i need to do?:

@manuel yes but also may the better way to install grub onto dualboot bios system with win10 as second OS, as in my experience win10 updates will do not work in some cases if boot is not owned by window. (millennium updates)

“will do not work in some cases if boot is not owned by window. (millennium updates)”

Which is what you advised and one of the things I’m trying to avoid.

Yes i do have win10 on a seperate disk to avoid this problem, on another system i use a mmc-disk for grub…

And it is also possible to use a windows-dvd to reset to windows mbr if there is one of this updates and write grub back after updating…

And of caus you can use legacy-grub also or syslinux.

@joekamprad said in Dual boot alongside W10 on BIOS system: What do i need to do?:

Yes i do have win10 on a seperate disk to avoid this problem, on another system i use a mmc-disk for grub…

And it is also possible to use a windows-dvd to reset to windows mbr if there is one of this updates and write grub back after updating…

And of caus you can use legacy-grub also or syslinux.

Thats my issue, then. I’m on a laptop and I have only one HDD.

This is how the space is allocated on it:
https://imgur.com/a/C5q9T
And this is what Cnchi shows me when I’m trying to install:
https://imgur.com/a/PZWfT

following this the mbr i’ll be overwritten, right?
And I’ll have to boot into antergos and mess with os-prober and what not to make windows bootable again? is that right?

yes mbr will be overwritten if you choose to install bootloader, but mostly windows will be detected and bootable from grub-bootloader aside from antergos… you can also choose to do not install bootloader, and use another way to do so.

But it is not possible with installer, it will need to be done by booting again to installer and chroot into installed antergos…

@joekamprad said in Dual boot alongside W10 on BIOS system: What do i need to do?:

yes mbr will be overwritten if you choose to install bootloader, but mostly windows will be detected and bootable from grub-bootloader aside from antergos… you can also choose to do not install bootloader, and use another way to do so.

But it is not possible with installer, it will need to be done by booting again to installer and chroot into installed antergos…

So… Is it save to install grub following the Cnchi installer, then I’ll boot into Antergos and os-probe to find the W10 install and be able to boot into W10 again?

IRRC there’s something about doing this in UEFI systems in a tutorial you contributed in the Antergos Wiki. So It’ll work for BIOS too?

One more thing that got me worried was when I read the GRUB entry on the Arch Wiki:
https://wiki.archlinux.org/index.php/GRUB

This part specifically:

Master Boot Record (MBR) specific instructions
Usually the post-MBR gap (after the 512 byte MBR region and before the start of the first partition) in many MBR (or ‘msdos’ disklabel) partitioned systems is 31 KiB when DOS compatibility cylinder alignment issues are satisfied in the partition table. However a post-MBR gap of about 1 to 2 MiB is recommended to provide sufficient room for embedding GRUB’s core.img (FS#24103). It is advisable to use a partitioning tool that supports 1 MiB partition alignment to obtain this space as well as to satisfy other non-512 byte sector issues (which are unrelated to embedding of core.img).

I don’t know exactaly what I should do (considering I can’t repartition now since the windows Partition is in the beggining of the drive, and my only option would be to repartition considering this post-mbr gap, reinstall windows and then install antergos), or if I should worry about this at all.

@namelessking
It is possible to write grub to the MBR of another disk, like a cheap USB stick. Then you would need to keep that stick attached to your computer every time when you want to boot to Antergos. And the MBR of your main disk (/dev/sda) is not overwritten.

But how to do that? Just attach the extra USB stick to your machine before starting the Antergos install. Then Cnhci should see it and allow putting grub to its MBR.

Considering what has been already discussed on this thread, it seems for me the only possibility to solve the case.

@manuel said in Dual boot alongside W10 on BIOS system: What do i need to do?:

@namelessking
It is possible to write grub to the MBR of another disk, like a cheap USB stick. Then you would need to keep that stick attached to your computer every time when you want to boot to Antergos. And the MBR of your main disk (/dev/sda) is not overwritten.

But how to do that? Just attach the extra USB stick to your machine before starting the Antergos install. Then Cnhci should see it and allow putting grub to its MBR.

Considering what has been already discussed on this thread, it seems for me the only possibility to solve the case.

It’s not pratical for me to use a USB stick to do this. Unfortunately.

It’s not a problem if I have to overwrite the windows mbr. I just want to configure in a sane way and make it work. uhm

@namelessking
OK, then it is easy. You already have Windows installed? Then

• Create a Windows recovery disk, just in case you need to recover Windows MBR.
• Install Antergos and let Cnchi overwrite the MBR in /dev/sda.

Now you should be able to boot to Antergos and Windows from the grub boot menu.
But if Windows is not in the menu, you can give a command

grub-mkconfig -o /boot/grub/grub.cfg

and reboot. Now you should see Windows in the grub boot menu.

@namelessking also possible from BIOS-Systems https://antergos.com/wiki/miscellaneous/how-to-fix-grub-with-bios-boot/

But there is no problem boot into windows when you install grub from antergos install, it uses os-prober already and will add a working windows entry. Only on some systems this will fail and you need to fix this by rerunning grub-mkconfig adter installation from running Antergos… it is only a problem if you have more then one Linux installtion.

@manuel @joekamprad Thanks both of you. I’ll try this soon.

@manuel will a standard w10 install usb stick work for the recovery? I have one already, But if it’s not suitable for it I’ll just format it and turn into a recovery one.

@namelessking
I believe it is suitable for recovery, too, but I must admit I’m not sure.

yes i use the standard installer iso from windows 10 to recover my win10 boot here.
You need only the right commands and use the CMD inside.