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KvK 01-18-2012 06:59 PM

Installing OS on external hdd w/o changing MBR on Primary hdd
I have a laptop that I dual boot with Windows-7 and Ubuntu-11.04. I want to try out other distros and systems as well. For this, I have a new procured a new hard drive on which I want to install the following OSs - Slackware, Fedora, Solaris, a couple of BSDs, and maybe a few more. I already run Windows-7, OpenSuse on a KVM inside Ubuntu and am running out of space so running these on VM is not an option. I want to run them natively and if I have space, maybe do a VM installation on the new hdd as well. (There will be too many OSs to choose from!!)

So if I install these (or any) OS on the external hdd with the Primary hdd 'still connected', will it overwrite the MBR on the Primary hard drive? I know that in a case I mess up the MBR, I can redo the GRUB on the Primary OS. But I want the probability of that happening.

And forgot, just to let you know, I can connect the external hdd via SATA or eSATA. So USB limitations should not be an issue.


Janus_Hyperion 01-18-2012 07:22 PM

There is something called chainloading. You can install GRUB of individual operating systems on it's own partition without touching the MBR. This would be really useful in your case as I see it. What I do not know, however, is whether that can be used for USB hard disks also.

Here is a link that might be of use. Chainloading

jefro 01-19-2012 04:01 PM

When you install your OS as a native install they usually offer you the option to put the loader in some place. You want to put the loader on the external drive. Then when you want to boot to it, you select either the boot device in bios or select it with a boot option key.

If you want you can install VM's to the external all day long too.

KvK 01-19-2012 05:59 PM

Thanks Jefro!
That sounds as a viable option. Just to make things clear, do the '/boot' for each OS need to be a separate one or can I make a single BOOT partition and use it for all other OS at the '/boot' (w/o formatting of course)? Sounds trivial but basically the above query simply means - If I add a 2nd and a 3rd OS, will it rewrite the boot loader?
P.S. - Chainloading - Thats a concept I'll play with someday. But isn't that a post-installation procedure?


jefro 01-20-2012 03:05 PM

In a modern bios you can select which drive is the first boot order. In the olden times you only had the ability to wire a drive or jumper a drive. Bios boots and orders drives based on how it views them. On new systems you can tell bios to change how it see's first bootable drive.

In all cases you need to be very careful with boot loaders. Three issues are present. One is the version. Some must have a version of a special loader such as grub2. Some don't care. This would be a case where you would have to chain load from one loader to another version.

Some OS install programs are not clear or don't give you a good choice to know how to install a loader.

Issue to remember is bios loads the first bootable partiton (bootloader) in it's known order. Usb could show up under real hard drive order.

Lastly is a long time ago there were programs to select boot order. I am sure they are around and still work. They can load like 97 OS's of almost any type as I recall.

KvK 01-23-2012 02:44 AM

Okay. After 24+ hrs of digging around and installing/deleting partitions and OSs, I finally have a working configuration. I was too much of a chicken to mess around with my new thinkpad which hosts all of my work and hence cancelled the external HDD installation and instead installed OS on an internal HDD on Dell XPS. Following is my confuguration:
sda1 - Primary - ??? (Was planning to put /boot here of all OS but didnt do it. I have no idea whats here now, 30mB consumed)

sda5 - Logical - Swap
sda6 - Logical - Slackware 13.7
sda7 - Logical - Fedora 16
sda8 - Logical - LinuxMint debian (12)
sda9 - Logical - Opensuse 12.1
sda10- Logical - Solaris 11 (Was Working, but grub2 cant see it, Failed??!! See details below)
sda11- Logical - Damn small Linux (None of the dsl.iso work, still empty)
sda12- Logical - BackTrack
sda13-16 Logical - Ubuntu 11.04

sda3 - Primary - Data
sda4 - Primary - FreeBSD 9 - "FAILED", now using as Virtual Space

* FreeBSD and Solaris NEED Primary Partition!!

I did all the partitions using slackware, and after my 4th OS I realised I need a primary for both of them. Also I am new to Slack, so didnnt knew the setting the align partitions to cylinder. As a result FreeBSD kept on giving me warnings for sda2-4. I made some free space between sda3 and sda4. Only then it stopped the messages for sda4. Spent 10+ hrs on BSD alone. Eventually I gave up and now will boot it on a VM.

I was able to log onto Solaris 11 and it was working. But after I installed a new OS, I couldn't see it. I tried chainloading with GRUB in Ubuntu, but of no avail. In fact the partition type is seen as 'Unknown'. Also, All of the dsl.iso that I downloaded were corrupted and hence haven't installed it.

Finally the most important part - BOOTLOADER - What I did was if the OS offered me to install its bootloader, I denied it and did a clean install for the final (ubuntu for me) one only. Grub2 dies a great job in automatically getting boot info from the other installations.


KvK 01-25-2012 07:00 PM


Epic Update! The chainloading thing is awesome. I can see Solaris 11 on Grub now. All I did was reboot a couple of times, and now it shows up!!

FreeBSD is the only hiccup now!

Thanks again for your replies

otoomet 01-26-2012 09:20 AM

KvK -- you may check if your computer supports efi and gpt (guid partition tables). In that case you may spend another 24h and create tons of primary partitions. With some good luck, you get both solaris, bsd & firends easily up in this way ;-)

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