Hi guys,
I am trying to dual boot centos and ubuntu. I have tried installing centos first and ubuntu second, however when i install ubuntu i don see my cenos in ubuntus grub. The same goes for vice versa when I install ubuntu first and centos second. I don see ubuntu in the centos grub

I then tried not installing grub while installing the second operating system so the first grub remains but that did not help.

Now I am using centos grib but I dont know how to modify my grub.conf to include ubuntu as ubuntu10.4 used grub 2 and centos5.5 uses grub.

While installing ubuntu second I did not install grub and I got this message --> you will need to boot manually with the /vmlinuz kernel on partition /dev/sdb1 and root=/dev/sdb1 passsed as kernel argument. I dont know what this means and how to do that.

[root@labstation etc]# fdisk -l

Disk /dev/sda: 250.0 GB, 250000000000 bytes
255 heads, 63 sectors/track, 30394 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sda1 * 1 13 104391 83 Linux
/dev/sda2 14 6387 51199155 83 Linux
/dev/sda3 6388 12761 51199155 83 Linux
/dev/sda4 12762 30394 141637072+ 5 Extended
/dev/sda5 12762 14036 10241406 83 Linux
/dev/sda6 14037 14546 4096543+ 82 Linux swap / Solaris

Disk /dev/sdb: 250.0 GB, 250000000000 bytes
255 heads, 63 sectors/track, 30394 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sdb1 1 29172 234315776 83 Linux
/dev/sdb2 29172 30395 9822209 5 Extended
/dev/sdb5 29172 30395 9822208 82 Linux swap / Solaris


[root@labstation etc]# cat /boot/grub/grub.conf
# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE: You have a /boot partition. This means that
# all kernel and initrd paths are relative to /boot/, eg.
# root (hd0,0)
# kernel /vmlinuz-version ro root=/dev/sda5
# initrd /initrd-version.img
#boot=/dev/sda
default=0
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title CentOS (2.6.18-194.3.1.el5PAE)
root (hd0,0)
kernel /vmlinuz-2.6.18-194.3.1.el5PAE ro root=LABEL=/
initrd /initrd-2.6.18-194.3.1.el5PAE.img
title CentOS (2.6.18-194.el5PAE)
root (hd0,0)
kernel /vmlinuz-2.6.18-194.el5PAE ro root=LABEL=/
initrd /initrd-2.6.18-194.el5PAE.img

[root@labstation etc]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda5 9.5G 1.3G 7.8G 15% /
/dev/sda3 48G 180M 45G 1% /home
/dev/sda2 48G 180M 45G 1% /opt
/dev/sda1 99M 17M 78M 18% /boot
tmpfs 2.0G 0 2.0G 0% /dev/shm

Easiest will be to leave Centos in place and reinstall grub2 in Ubuntu - or just reinstall Ubuntu again. Choose to install grub[2] to the root partition.
Then add the following to the end of your Centos grub.conf (adjust for appropriate partitions)

What is
root (hd1,0)
root (hd0,0)
Why did you choose hd1? Can you please explain

Please guys im stuck. I have reinstalled ubuntu and i have grub 2 right now. when i run the update-grub command i get

Generating grub.cfg ...
Found linux image: /boot/vmlinuz-2.6.32-21-generic-pae
Found initrd image: /boot/initrd.img-2.6.32-21-generic-pae
Found memtest86+ image: /boot/memtest86+.bin
Found CentOS release 5.5 (Final) on /dev/sda5
done

However when I reboot i do not see CentOs in the menu. Please any suggestions. Thanks

* What version of grub are you installing 1 or 2
The configuration is different on each.

(hd?,?) stands for (hd[drive number], [partition number]) they both start counting at 0

I reinstalled Ubuntu 10.4 and it installed grub 2