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Grub2 Options ? Advise needed ...


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#1 TW.4T

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Posted 17 January 2013 - 12:25

Hi, at the moment I have a Triple boot config consisting of Win7, Win8 and Win7. This is how I want it and I like it this way. So, my question is, if I install a new Linux distro is it possible for me to put Grub2 onto a USB stick? This way ( i think ) if I boot my laptop without the USB inserted it will show the Windows boot loader but if I boot with the USB inserted it will load up Grub2 and allow me access to Linux. I'm thinking that this has a 2 way benefit, one it will not screw with the Windows loader and secondly it will protect access to Linux if the USB stick is not present. Is this possible and if so is it just a case of selecting the USB when it comes to the Grub2 install or am I way off the mark? Many thanks.


#2 Haggis

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Posted 17 January 2013 - 12:32

Hmmm i am sure this is possible thinking about it

but i have no idea how to do it myself

Interesting concept though and i would love to know how to do this too

#3 n_K

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Posted 17 January 2013 - 12:44

Yes it is possible, just install your linux distro as normal but do NOT install a boot-loader, or, when booted up mount the USB as /boot, e.g.
mount /dev/sdf1 /boot
and install as normal and I would think it'd install the grub mbr to /dev/sdf.

#4 +Karl L.

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Posted 17 January 2013 - 21:12

n_K is correct. You can choose which disk to install the bootloader to from most Linux distro's installers, but its easy to miss the prompt.

You might also consider downloading Super Grub2 Disk and putting that on your flash drive or a CD. It will let you boot most Windows or Linux installations even if the MBR is missing or corrupt.

#5 firey

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Posted 17 January 2013 - 21:42

Having not done this myself, I just want to be clear. I could install the distro of my choice to a partition on my Hard-Drive. And not install grub. That way I can still book directly to windows. However I could install grub onto my USB stick and have it so that if the USB stick is inserted on boot, it will give me the grub boot menu letting me pick either windows or linux?

#6 +Karl L.

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Posted 17 January 2013 - 22:12

Having not done this myself, I just want to be clear. I could install the distro of my choice to a partition on my Hard-Drive. And not install grub. That way I can still book directly to windows. However I could install grub onto my USB stick and have it so that if the USB stick is inserted on boot, it will give me the grub boot menu letting me pick either windows or linux?


That is correct. Super Grub2 Disk offers an easy way to do auto-detection of installed operating systems, but you could just as easily have a GRUB installation on a flash drive with a custom menu allowing OS selection. Although there are many variations of methods to accomplish this, everything other than the aforementioned Super Grub 2 Disk require some work in terminal an a minimal working knowledge of GRUB menu scripting. Since most people don't want to do this, as it creates more of a hassle, no distro that I know of makes it "1-click" or "2-click" simple to accomplish. That's why I didn't recommend anything else to the OP. Based on your other posts, I believe that you would be able to pull off a more elegant solution. Let me know if you want me to provide such instructions.

#7 firey

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Posted 18 January 2013 - 01:30

That is correct. Super Grub2 Disk offers an easy way to do auto-detection of installed operating systems, but you could just as easily have a GRUB installation on a flash drive with a custom menu allowing OS selection. Although there are many variations of methods to accomplish this, everything other than the aforementioned Super Grub 2 Disk require some work in terminal an a minimal working knowledge of GRUB menu scripting. Since most people don't want to do this, as it creates more of a hassle, no distro that I know of makes it "1-click" or "2-click" simple to accomplish. That's why I didn't recommend anything else to the OP. Based on your other posts, I believe that you would be able to pull off a more elegant solution. Let me know if you want me to provide such instructions.


well, I would be going with arch, and part of the guide is installing grub. I can probably just modify that step so that instead of installing to /dev/sda1 it installs it to a usb mounted partition. I'll give it a shot tomorrow and let you know

#8 n_K

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Posted 18 January 2013 - 02:39

Yep. When installing arch, do NOT make a seperate boot partition on your hard drive, make that on the USB as ext2 and mount that as /mnt/boot, so eg;
mount /dev/sda2 /mnt
mount /dev/sdf1 /mnt/boot

then in the grub commands, use the sdf or USB drive, I'm not sure if you even need to provide the drive anymore or if grub picks it up from what device /boot is mounted on.

#9 +Karl L.

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Posted 18 January 2013 - 04:55

Yep. When installing arch, do NOT make a seperate boot partition on your hard drive, make that on the USB as ext2 and mount that as /mnt/boot, so eg;
mount /dev/sda2 /mnt
mount /dev/sdf1 /mnt/boot

then in the grub commands, use the sdf or USB drive, I'm not sure if you even need to provide the drive anymore or if grub picks it up from what device /boot is mounted on.


That is one way to pull it off, but there is a slight problem with that method. Namely, since your kernel is located on a partition on your flash drive, you will need to have it installed and mounted each time you perform a kernel update. Furthermore, when you install a new kernel in most distributions (although not Arch or Gentoo AFAIK), your grub.cfg will be regenerated - potentially causing some inconsistency.

A better method would be to leave /boot on your hard drive, and opt not to write GRUB to the MBR. Then install GRUB to the EXT2 partition on your flash drive, and write a grub.cfg that will automatically launch GRUB from your hard disk (via core.img or by loading the config file). The advantages of this method are that you don't need to have the flash drive mounted to perform kernel updates or anything else related to your system, just to boot it. You can safely remove the flash drive after Linux starts booting because init never mounts the flash drive or requires any files from it. Additionally, you have the option of limiting which installations it will automatically boot by probing for your /boot partition's UUID, including a custom "recovery kernel", or scripting other cool stuff. It takes more work than the first method initially, but its easier in the end (not to mention more elegant, which I believe is the Arch philosophy - and a leading reason why pacman should be put out of its misery).

#10 tim_s

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Posted 19 January 2013 - 00:29

it will protect access to Linux if the USB stick is not present.


If you have reached a point that someone wants access to your machine and is willing to spend the effort to by-pass any passwords, this will not be enough. The file system needs to be encrypted, sure keep the USB to kick start the process but only know this adds only a layer of irritation. Most likely an attack would occur while the OS was in operation or the machine has left the premise and they probably would not make use of your hardware anyways.



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