How do I manage my partitions to install Fedora Core 4 alongside with an existing install of CentOS

What do you want to do?
How are partitions defined now?
What do want to end up with when done?

Quick note when dealing with Redhat/Fedora/Centos/Enterprise distros, since Centos is installed already then modify /etc/fstab and replace the LABEL= with thier true /dev points. You can get that info from /etc/mtab. Also do the same to /boot/grub/grub.conf.

Reason if you what to create two seperate distros on 2 seperate harddrives and you create a /usr on one and a /usr on the other then the system gets confused on mounting. For some reason it tries mounting both on the same mount point even though you only need one. Defining true mount devices fixes the confusion.

Im not good with partitioning and had used automatic partitioning for installing CentOS, Why do you need to modify the fstab file and the grub.conf.

So as an end result I want to end up with CentOS or fedora 4 on my grub boot loader menu

Do you wish to end up with two seperate operating systems running on thier own partitions?
Are they both going to remain on the same drive?

If on the same drive the best and easiest way is to create a /boot partition about 100mb. This one will be used by both OSes. Then create a seperate / partition for each OS. And then might be best to have a partition that is used between both call it /storage. Also include a swap partition of about 256meg to 512 meg. So the end result is. Make any larger, I do not konw the drive size you are working with.

/dev/hda1 /boot used by both. 100mb
/dev/hda2 / for one OS. 12 gig if using full install.
/dev/hda3 / for another OS. 12 gig if using full install.
/dev/hda5 /storage for both. About 6 gig is size
/dev/hda6 swap. About 256mb to 512mb and used by both.

With this setup you will have no conflicts on apps like KDE when updating. If you used common partitions for say /usr or /opt then when you update KDE on one of them it will more than likely not work on the other do to dependencies issues. Then you have conflicts in home directory of hidden config files from one version change to the other until both are at the same level.

Now for the fstab issue you cannot have to partitions pointing to /. The issue with the redhat-Centos is they use a scheme using LABELS. You just need to open /etc/fstab and /etc/mtab to understand.

Once you installed the first distro you need to modify /etc/fstab to point to the correct partition to /dev. At this time you could have created the 2nd OSes partition but at this time you do not mount it. Install the second OS and more than likely you will have to enter rescue mode or boot with a live CD and modify the /etc/fstab of the second OSes /.

You can mount the others OS / partition if you wish but you need to mount it to say /second_os directory.

Examples of fstab for each OS install using references above.
Fedora OS
Centos OS
I hope this will help.
Brian1

Thank you all very much, I will try it today.