Dual Boot UEFI Window 10 Centos 7.4 - helpful hints
Posted: 2017/10/12 17:26:31
Even with all the help available online, I think I almost broke the record for number of successive installs of BOTH win 10 & CentOS in trying to get dual booting to work for me. Trial and error (rinse repeat) plus reexamining various forum posts sprinkled to and fro I FINALLY was able to dual boot my new windows 10 and CentOS 7.4 from fresh installs! Yay.
I made a bunch of mistakes mostly fueled by ignorance, anyway as a possible help to others out there stumbling around in the dark, perhaps my notes here will help flip on the light-switch and make this process easier for someone else.
So here's my setup, nothing particularly special:
ASUSTeK SABERTOOTH X79 with an Intel i7-3930K PC, installing both OS's onto a 1Tb sata drive from DVD install media (in both cases).
Before embarking on this task I upgraded the BIOS to pretty much the latest available (v4701 on the Asus site - via a USB stick - simple process).
Since Centos7.4 can handle UEFI without problem I did NOT turn off "Secure Mode", in other words, UEFI mode is active through the BIOS. Furthermore, there is something available called CSM (Compatibility Support Module) where I flipped all treatment of various media to prefer UEFI over "Legacy oprom".
I followed the advice of folks online to FIRST install Windows 10, THEN CentOS. Here's a CRITICAL bit of information: You NEED make sure Windows 10 is installed in UEFI mode, and how you do (or how I did) that was to insert the disk at boot time, then jump into the BIOS and then there's a way to select the Boot Media explicitly. I was given two choices to boot from the SATA DVD drive, i) regular looking mode where it just lists the SATA port ("P4: ATAPI ..." in my case), and choice ii) the SATA DVD-drive label is prefixed with UEFI <- USE THAT ONE, otherwise windows won't install in UEFI mode.
Prior to this I had used my CentOS install disk's recovery mode to give me a shell where I could use "gdisk" to make the 1Tb disk use a gpt partition table (as opposed to DOS). It's possible if you start with a DOS partition table that the Windows 10 installer will flip it for you, but I had already (in my many failed trials) apparently tried to install non-UEFI Windows 10 onto a gpt partition tabled disk and it simply refused to deal with it (I think... I did so many variations that it's hard to recall all the road blocks).
So, proceed with the Windows install - it will take over the whole disk. Once it's all installed free up some space with "Shrink" via the disk management tools (lots of help to do this online). I freed up 220 Gb leaving ~740 Gb for Windows.
Once this is done, reboot, and with the same proceedure, launch your CentOS 7.4 DVD installer via the BIOS, explicitly making sure to launch the UEFI choice for the DVD-SATA-drive.
The following link is really useful especially IF you do the above steps because then the instructions on the web-page will mirror what you see on your screen - otherwise, it's going to be different, and different is BAD. (I'm fuzzy on the whole Good-Bad thing, ... OK, Imagine every molecule in your body simultaneously exploding at the speed of light... Total protonic reversal - OK that's "Bad" THX Egon!)
https://www.tecmint.com/install-centos- ... -firmware/
If all went well, you should simply see CentOS AND Windows boot loader as options on your boot screen. Nothing else should need to be done! I hope that helps - It will probably help me again in a year when I completely forget this entire process.
Cheers,
James.
I made a bunch of mistakes mostly fueled by ignorance, anyway as a possible help to others out there stumbling around in the dark, perhaps my notes here will help flip on the light-switch and make this process easier for someone else.
So here's my setup, nothing particularly special:
ASUSTeK SABERTOOTH X79 with an Intel i7-3930K PC, installing both OS's onto a 1Tb sata drive from DVD install media (in both cases).
Before embarking on this task I upgraded the BIOS to pretty much the latest available (v4701 on the Asus site - via a USB stick - simple process).
Since Centos7.4 can handle UEFI without problem I did NOT turn off "Secure Mode", in other words, UEFI mode is active through the BIOS. Furthermore, there is something available called CSM (Compatibility Support Module) where I flipped all treatment of various media to prefer UEFI over "Legacy oprom".
I followed the advice of folks online to FIRST install Windows 10, THEN CentOS. Here's a CRITICAL bit of information: You NEED make sure Windows 10 is installed in UEFI mode, and how you do (or how I did) that was to insert the disk at boot time, then jump into the BIOS and then there's a way to select the Boot Media explicitly. I was given two choices to boot from the SATA DVD drive, i) regular looking mode where it just lists the SATA port ("P4: ATAPI ..." in my case), and choice ii) the SATA DVD-drive label is prefixed with UEFI <- USE THAT ONE, otherwise windows won't install in UEFI mode.
Prior to this I had used my CentOS install disk's recovery mode to give me a shell where I could use "gdisk" to make the 1Tb disk use a gpt partition table (as opposed to DOS). It's possible if you start with a DOS partition table that the Windows 10 installer will flip it for you, but I had already (in my many failed trials) apparently tried to install non-UEFI Windows 10 onto a gpt partition tabled disk and it simply refused to deal with it (I think... I did so many variations that it's hard to recall all the road blocks).
So, proceed with the Windows install - it will take over the whole disk. Once it's all installed free up some space with "Shrink" via the disk management tools (lots of help to do this online). I freed up 220 Gb leaving ~740 Gb for Windows.
Once this is done, reboot, and with the same proceedure, launch your CentOS 7.4 DVD installer via the BIOS, explicitly making sure to launch the UEFI choice for the DVD-SATA-drive.
The following link is really useful especially IF you do the above steps because then the instructions on the web-page will mirror what you see on your screen - otherwise, it's going to be different, and different is BAD. (I'm fuzzy on the whole Good-Bad thing, ... OK, Imagine every molecule in your body simultaneously exploding at the speed of light... Total protonic reversal - OK that's "Bad" THX Egon!)
https://www.tecmint.com/install-centos- ... -firmware/
If all went well, you should simply see CentOS AND Windows boot loader as options on your boot screen. Nothing else should need to be done! I hope that helps - It will probably help me again in a year when I completely forget this entire process.
Cheers,
James.