How to make double boot (CentOS & Ubuntu)?

January 12, 2011 at 00:43:12
Specs: Ubuntu
Hi all,
I had a CentOS installed on my PC when I decided to install Ubuntu 10.04.
I took a new HD, and installed Ubuntu on it. During the instalation both the HD were connected.
Before the instalation I had the following partitions on my old HD:
1) 53GB - data
2) 100MB - boot
3) 100GB - data2
4) 350GB - CentOS
After the instalation, I see the first 3 partitions, but not the forth. The new HD with Ubuntu on it I see also.
The questions is:
1) Why I don't see the CentOS partition? How can I recover it?
2) Why the new HD is not bootable? To boot I need the old HD to be connected. Probably the "boot" partition on the old HD point the system to boot from the new HD. How can I make the new HD bootable with no dependence on the old HD?

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#1
January 12, 2011 at 05:28:17
need to see the output of fdisk -l-uthe l is a small L.

(How can I make the new HD bootable with no dependence on the old HD) it would seem that grub was installed onto the MBR of the old hdd. You need to install grub to the mbr of the new hdd, how to do that depends on what grub in use 'grub legacy version 0.9x or grub2 version 1.xx'.


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#2
January 12, 2011 at 06:01:48
The first issue was solved by installing lvm2 package.
About the second problem, I'd installed another Ubuntu on the new HD (on different partition) when the first HD was disconnected, and now I can boot from the new HD and choose which Ubuntu to load.
So, if both the HDs connected, I can boot from the new one and choose between the two Ubuntus. Also I can boot from the old HD, but there I can boot with the first Ubuntu (I'd installed on the new HD) only. I have no option for CentOS.
The questions are:
1) What will be if I will install different OS on (or even just erase all the data from) the second partition on new HD? Could I still boot from this HD?
2) How (if at all) can I boot with CentOS?

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#3
January 12, 2011 at 18:25:21
(What will be if I will install different OS on (or even just erase all the data from) the second partition on new HD? Could I still boot from this HD?) If you erase the new hdd, you will not boot from the new hdd. You can install a different linux and be able to boot.

It is not difficault to add a entrie to the boot menu, but the how will depend on which grub is in use. Look in /boot/grub/ of the Ubuntu install are there less then 15 files ? or 20+ files ?

Also mount and look at {2) 100MB - boot} /boot/grub

If 20+ files you are useing grub 2 read both links below:
https://help.ubuntu.com/community/G...
http://www.dedoimedo.com/computers/...

If less the 15 files you are useing grub legacy have a read:
http://members.iinet.net.au/~herman...


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