MBR Dilema

HungGarTiger · Posted: Mon Jul 21, 2014 8:24 pm Post subject: MBR Dilema

Hi Guys,

I'm currently building a new computer system and I want to try a dual boot setup, I plan to have 3 SSD's running and 1 1TB Data drive

1. Windows - primarily for games
2. Gentoo/Linux Experimental - Testing Gentoo updates before pushing to stable or trying out new Linux Distros and being able to wipe and forget
3. Gentoo Stable - Everyday use
4. Data - storing everything else, accessable by all 3 drives

My problem is, I've only ever run Linux on a single disk. How would I go about ensuring all 3 OS are bootable from GRUB 2? /boot will be on the same partition as / on each Linux SSD, only 3 partitions will be SWAP, / and /home. Should I dedicate the MBR in Gentoo Stable to containing GRUB 2? Will I need to look into LVM to make sure they all function correctly?

Sorry for the probably quite basic question, I'd appreciate any advice in this area as I have 0 experience in it.

The Doctor · Moderator Joined: 27 Jul 2010 Posts: 2678

The fact that they are on separate drives shouldn't affect anything, but 2) is not something you should put on an SSD since it will get rewritten quite often and will have a short life expectancy.

A much more elegant solution to that problem is to use a kvm or virtualbox solution to do the testing in a virtual environment. This includes the ability to use snapshots etc. This not only reduces wear but allows you to keep multiple testing platforms in place. Personally, I would ditch the 3rd SSD and replace it with another 1 TB drive to hold the data for multiple virtual machines.

And if this is a new computer you would almost certainly be better served by using GPT partitions and the built in EFI boot manager or rEFInd according to taste. This is particularly true if you are going to use Windows 8. One advantage of using the EFI boot loader is that the boot process for the default choice won't be slowed down for a boot menu unless you enter the boot menu in a similar way to entering the BIOS configuration screen.
_________________
First things first, but not necessarily in that order.

Apologies if I take a while to respond. I'm currently working on the dematerialization circuit for my blue box.

HungGarTiger · Posted: Mon Jul 21, 2014 8:51 pm Post subject:

The Doctor · Moderator Joined: 27 Jul 2010 Posts: 2678

ct85711 · Veteran Joined: 27 Sep 2005 Posts: 1791

I know when I installed Windows 7, the cd by default would only install to the MBR (and through a fit because it saw Gentoo was already installed and won't do anything because of that). I had to setup a usb boot drive, to get the windows installer to install in UEFI, and it didn't care then that Gentoo was installed. It saw that I already had a ESP boot drive on one of the drives and was happy enough to use that. Had to tell my bios to switch the default EFI loader back to linux, and grub2 gladly saw the windows efi loader, and added it to the boot screen afterwards. I couldn't say how easily grub2 will play with 2 different copies of Gentoo; so you have have to fight with it to tell it which root drive to use.

creaker · l33t Joined: 14 Jul 2012 Posts: 651

I have 3 Linux installation + 2 Windows installation + LinuxMint Live DVD iso. All these systems located on two drives and Grub2 manages all these systems.

/dev/sda1 - Gentoo Linux (Grub installation and /boot directory are here)
/dev/sda2 - Gentoo Linux (No Grub installation)
/dev/sda3 - Windows 7
/dev/sda5 - File Storage Partition

/dev/sdb1 - Windows XP
/dev/sdb6 - Gentoo Linux (No Grub installation)
/dev/sdb7 - File Storage Partition.

Grub binaries are installet at /dev/sda mbr.
If you planning to install your Linux with /boot at the same drive with Winsows, Windows should be installed in the first place because it will rewrite mbr.
If you planning to dedicate a whole SSD for Windows (or Windows + File Storage) this case no matter when you will install Windows. You have just to set SSD wint bootable Linux as a primary boot device. I think it is better option (to separate Windows (e.g. at /dev/sdb) from Linuxes (e.g. at /dev/sda)), if you will get some trouble with Grub bootloader (/dev/sda) you will be able to use Windows still (using Windows bootloader at /dev/sdb mbr)

HungGarTiger · Posted: Tue Jul 22, 2014 7:35 am Post subject:

The Doctor · Moderator Joined: 27 Jul 2010 Posts: 2678

I would put windows on sda and install it first. It won't respond well having its designation change and installing it first insures that it won't damage anything. You can always set the bios to boot from sdb or sdc.

Also, all your Linux partitions should share swap since no persistent data is stored there and it shouldn't be on an ssd for wear issues. You should probably split /usr/portage off to and put /tmp and /var/tmp in ram if you have enough. These 3 partitions will cause excessive wear to your ssd. Other than that your partitioning looks good.
_________________
First things first, but not necessarily in that order.

Apologies if I take a while to respond. I'm currently working on the dematerialization circuit for my blue box.

srs5694 · Posted: Fri Jul 25, 2014 1:08 am Post subject:

In my experience, GRUB 2 often falls down on more complex setups, with "more complex" being somewhat subjective, but ranging from two to four OSes and up. Basically, when using GRUB 2, you're forced to do one of two things:

Rely on GRUB 2's auto-detection, which usually works well for whatever distribution you're using, works OK for Windows, and is a crap shoot for anything else. If something breaks, fixing it is like walking on broken glass.
Disable GRUB 2's auto-detection and configure everything manually. This is possible, but it starts to become painful with a lot of distributions because you'll be constantly editing grub.cfg with kernel updates.

IMHO, GRUB 2 is the worst boot loader available for EFI-based systems. See my Web page on EFI boot loaders for my thoughts on them all. (Note that I'm not unbiased -- I maintain rEFInd, which I intend to work with minimal configuration effort.)

Windows 7 works fine with EFI, although as ct85711 noted, you may need to jump through some hoops to get its installation medium to boot in EFI mode.

ct85711 · Veteran Joined: 27 Sep 2005 Posts: 1791

Another thing to note, is that while you could do a hybrid setup (mixing mbr with efi boot); it is not supported too well on any system, and you'll more then likely have a larger headache than necessary try to do that. So I recommend sticking to only UEFI or MBR boot for everything and not mix between.

HungGarTiger · Posted: Fri Jul 25, 2014 9:36 pm Post subject: