Fixing dualboot with win10 and gentoo

[eamrhein]

I made the stupid mistake of thinking that if I remove my gentoo linux disk  and then installed windows on a separate disk I could plug my Gentoo disk back in and everything would be fine.
I tried using my liveusb and chrooting into my install and reinstalling grub, but when I reboot it still boots straight to windows. Any suggestions on how to fix this>

my motherboard is a MSI - h87-g43  with a haswell cpu and the settings are all default atm.

and my lsblk would look something like this

sda

     sda1 /boot
     sda2  swap
     sda3 /

Sdb  
     
    sdb1 small partition (something to do with windows boot i guess)
    sdb2 Windows Partition

sdc
    
    sdc1: Large Storage Parition

 

[jho]

when you install windows it makes itself your default boot option. you should be able to press a button (mine is f12) during boot up in order to bring up the boot menu or BIOS screen.

If you're not able to find the BIOS or boot menu, it might be because Windows doesn't ever do a full shutdown and instead just puts itself to sleep so that when you press power Windows just wakes up.

If this happens, I recommend shutting down windows, then holding onto the power button which will cause Windows to wake up, but keep holding onto the power button until your power is completely killed (15-20 seconds) and then after another 30 seconds power back on and you should be able to find the BIOS menu or boot select screen options

it's usually F12 or Esc. you can also google your exact motherboard model to find the correct boot key