Dualboot with windows 8 MBR

bluehippy · n00b Joined: 07 Sep 2014 Posts: 25

Hello everybody,

i have quite a huge problem with dualbooting gentoo and windows 8 installed in mbr mode. The problem is that GRUB2 doesnt recognise my windows installation and I really tried already many things to get it work. Here's what I did so far:

(1) Installed windows 8
(2) Installed Gentoo with the handbook (english version)
(3) Installed Grub2
(4) Windows wasnt recognised
(5) Did something I dont remember (Maybe reinstalling grub...)
(6) Dualboot was working :-DDDD
(7) Changed one kernel option related to networking and installed new kernel
(

Grub didnt recognised windows -> no dualbooting

To solve the problem I tried to reinstall grub2, os-prober (doesnt show anything), but nothing worked so far. Running grub2-probe on the windows booting partition to look for bootmgr only gives an

charles17 · Advocate Joined: 02 Mar 2008 Posts: 3664

What is the output of

Fitzcarraldo · Posted: Sun Sep 07, 2014 9:30 am Post subject:

Also, after building the new kernel, did you check the contents of /etc/default/grub (especially GRUB_CMDLINE_LINUX) and then run the grub2-mkconfig command to regenerate the grub.cfg file?

bluehippy · n00b Joined: 07 Sep 2014 Posts: 25

hi, thanks for the help

Roman_Gruber · Posted: Sun Sep 07, 2014 9:41 am Post subject:

Did you overwrite your windows partition?

You may write down here your partition layout please. starting with

/dev/sdx /mount_point file_system (description what you need it for)

e.g.

/dev/sda1 /boot /ext2 (needed for grub to boot)

you can also use a gparted livecd and do the partition layout there. please consider that you can move partitions with gparted too.

bluehippy · n00b Joined: 07 Sep 2014 Posts: 25

Not sure if the windows partition was overwritten. I didnt touched it manually, maybe grub touched it.

Partition layout:

/dev/sda1 windows/system ntfs partition was created during the inital windows installation size 350MB
/dev/sda2 windows/c:\ ntfs my windows installation size 240GB
/dev/sda3 lvm LVM for linux installation. I use an LVM to be able to easily change the size.

LVM:

/dev/mapper/vg0-grub no-mount grub <- I intended this as grub partition, but no idea if grub uses it (grub was installed with grub-install /dev/sda ) size 4MB
/dev/mapper/vg0-boot /boot ext2 boot partition, which has my kernel images (also the old one when windows was working) size 128MB
/dev/mapper/vg0-root / ext4 root with NO extra partition for /var, /tmp, or what so ever, size 50GB
/dev/mapper/vg0-home /home ext4 178GB
/dev/mapper/vg0-swap swap swap 4GB

charles17 · Advocate Joined: 02 Mar 2008 Posts: 3664

Maybe this wiki might help?

bluehippy · n00b Joined: 07 Sep 2014 Posts: 25

Thanks, I'll try.

There is a similar wiki on wiki.arch.org, but this one is much easier to understand.

bluehippy · n00b Joined: 07 Sep 2014 Posts: 25

the wiki asks to mount the windows partition, which fails for me with the error

jonathan183 · Guru Joined: 13 Dec 2011 Posts: 318

If you compiled it as a module then yes I think you should have a module called fuse, I think it gets loaded automatically by ntfs-3g when needed.
You could try

bluehippy · n00b Joined: 07 Sep 2014 Posts: 25

Actually some black voodoo magic happened...

I restarted the computer and booted from the Windows 8 DVD into the repair mode. There I opened a command shell, used a few times the commands "cd" and "dir" to see if I have a "boot" folder on my windows disk (There isn't any) and then rebooted. After the reboot grub recognised the windows installation (actually I set up an entry in /etc/grub.d/40_custom) and is now able to boot from both systems...

That's scary, just booting the windows dvd solved the problem for the moment...

When i'm back on gentoo, i'll post the output of the commands

thanks for the help