I have 2 distros sharing one drive, CentOS 5.6 and Ubuntu 11.04. I installed them both and had them running great. I installed CentOS 1st and then Ubuntu. I used the CentOS Druid Partitioner to create the partition table. Here's the partition table:

hdb1 /boot ext3 for centos kernel Primary
hdb2 /boot_ubuntu ext3 for ubuntu kernel Primary
hdb3 swap swap share between distros Primary
hdb4 extended extended extended partition Extended
hdb5 /var ext3 for centos only Logical
hdb6 / ext3 for centos root Logical
hdb7 /ubuntu ext3 for ubuntu install Logical
hdb8 /home ext3 shared between distros Logical

Then I installed ubuntu and everything was great. At some point I had the bright idea of messing around with compiz in Ubuntu and I thought I had broken the "user defined session" because it was blank when I would login to it. Finally I decided to reinstall ubuntu and reformat the ubuntu related partitions. I shouldn't have done that because the /home partition was shared with centos and it messed up my centos. I tried to fix it but only made it worse so I just reinstalled centos reformatting the related partitions and choosing not to install a bootloader. The install completed but didn't boot on restart. My clean install of ubuntu still boots but when I choose centos from the ubuntu grub menu it isn't able to boot, it goes to a black screen and hangs.

I checked my centos kernel version against the one in my grub and they matched. I checked my kernel version for centos from my ubuntu gui by looking here:

/media/_boot/config-2.6.18-238.el5

I usually have a clue as to what I need to do but this time I'm really stuck. I am however, confident one of you linux geniuses will give me a really simple solution that WILL make me look bad, so I'm not too worried.

(I'm planning to run apache on my centos for hosting some websites but for now I'm just trying to get my feet wet with linux, learn the fundamentals, important commands and essential trouble shooting. I will appreciate anyone's effort to spare me from zeroing out my drive and starting all over again! linux is really cool BTW and I'm having fun learning about it although I do wish centos looked as slick as Red Hat Enterprise.)

Believe it or not we need more info - go here and post the RESULTS.txt (no personal data)

My guess is that grub is using the UUID of your partition, which changed when you re-installed CentOS. Try re-generating the grub.cfg.

That was fast, thanks for the help! I attached the file, that script is awesome!

Attached Files

RESULTS.txt (19.4 KB, 26 views)

Tell me if you agree. I think the problem is that I choose not to install the bootloader for CentOS. I know the bootloader installs partly into the MBR and the rest goes in the boot sector;however, I thought I was covered by installing the bootloader for ubuntu alone. I was supposed to install the bootloader to my /boot for CentOS, wasn't I? Is that correct? That's all I can come up with, my knowledge is still pretty limited. If that's the case I have an idea what I should do but I'm not sure how to do it. I would appreciate it if someone could give me some detailed NOOB oriented instructions! BTW thank you for the help earlier, you are true professionals.

See @flamelord's post - the Centos root UUID is changed. That's why I love this script - it shows all the info you need.
@voltotron, try a "sudo update-grub" - it should rebuild that grub.cfg. If you get an update in the meantime it will do the update-grub for you and apparently the problem will appear to fix itself.

Yup that was pretty cool. I ran "sudo update-grub" from inside Ubuntu. It did update and it attempted to boot but it returned "kernal panic!", sounds alarming, LOL. I saw a post about it earlier but I disregarded it because it didn't apply. Any Ideas? I'm still trying to find the post you mentioned. Don't know if you'll need it but I'm going to run the script again and post results.

I ran the script again after running "sudo update-grub". here are the results. Don't know if it's supposed to be any different from the first results but I'm posting it just in-case. I'm going to find the post on the UUID now.

Attached Files

RESULTS2.txt (18.9 KB, 27 views)

Three above mine (in this thread) ... If you got a kernel panic, grub has done it's job. Start another thread with any (all) relevant info.

I'll do that. Thank you for everything and your quick replies. I've learned allot with your help.