hi
I install windows 8 after centos 6 but the centos cant boot up and i only access to windows 8.
how can I fix it for dual boot?

May just want to skip to the bottom of the article to the TipsAndTricks/ReinstallGRUB link.

Edit: I see you never got a proper welcome, so: Welcome to the CentOS fora. Please see the recommended reading for new users linked in my signature.

Hi "pschaff" and tanks.
I'm the beginier and cant fix it.
i run the "grub-install /dev/sda" in shell (live boot with DVD1 Centos) and I got an error.
how can fix it?

Hard to say without knowing what error you got. Did you do the chroot first?

yes I do it, but it got an error.
I dont remember what was it but when enter this "grub-install /dev/sda" the error comes different whit other commands that I enter.
excuse me for my bad enghlish.

No-one is going to be able to help you without knowing the exact commands that you issued and the exact error message(s) that you received. If you cannot remember them then you will need to repeat the process and write it all down and then post it.

Hi
I try it again and this error appear :
/dev/sda1 does not have any corresponding BIOS drive
what can I do?

Are you sure you want to install to /dev/sda1 and not to /dev/sda so it goes to the MBR? Might want to try

If more help is needed then please enable networking in rescue mode and show the results of

thank " pschaff" again
It's worked and my Centose boots up, but it couse a problem.
Windows 8 dosent exist on boot menu and I not able to boot Windows 8 any way.
what can I do?

Hi everyone.
after recovery Centos I got a big problem.
when I type command in rescue shell my external HDD was conected and I run this command "grub-install /dev/sdb1" several time and now the HDD dosent recognized in centos and known as unknown device. and this problem also happened to other partition on my internal drive.
Can I fix it?
My data lost? all of them?

Quote:
Is there not an entry "Other"? If so, that is Windows. You may want to edit /boot/grub/grub.conf to use a more descriptive title.

If not see Grub Installation for CentOS 5 and 6.

If still confused, show the current contents of /boot/grub/grub.conf and provide more information about your system by running "./getinfo.sh disk" and showing us the output file. This may also help with the external drive issue if it is connected.

unfortunately my windows partition also dont known in centos and like my external HDD dont recognize as a partition.
In disk utility its known as a unknown partition.
what can I do?
I also run the fdisk -l and got this

Disk /dev/sda: 250.1 GB, 250058268160 bytes
255 heads, 63 sectors/track, 30401 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xc96b2927

Device----Boot---Start-----End------Blocks-------Id----System
/dev/sda1-----------1------5737------46080000---83----Linux
/dev/sda2----------5737----5992-----2048000 ----82----Linux swap / Solaris
Partition 2 does not end on cylinder boundary.
/dev/sda3----*-----5992-----6037-----358400--- 7---- HPFS/NTFS
/dev/sda4----------6037------9817----30361600---7---- HPFS/NTFS


but it dosent exist in Computer on Centos.
I also run the grub-install /dev/sda3 and grub-install /dev/sda4 on the rescue shell.

What are you trying to accomplish by running grub-install on random partitions, such as your Windows NTFS partitions? It can't help anything and may be causing damage.

You still have not shown grub.conf, or anything about the external disk.

I connect my external HDD to another computer by windows.
In that computer my external HDD show as a partition in my computer but when I double click on it it say to format the device.
In the Disk Managment the hard show correctly and has an active partition.

Was the external hard disk formatted as NTFS? If so Windows probably did not take kindly to having grub boot code placed in its boot record. I'd try installing ntfs-3g following TipsAndTricks/NTFS and see if CentOS will mount it. You seem to have very little to lose by trying.

You may also want to try a google on NTFS recovery Linux tools.

I install these pakage befor and now I can mount any NTFS device like Flash drive, but My HDD dosnt work.
I think because I try to install grub boot loader to HDD and now it dosent work.
Is there any way to fix it?

Did you try the google search recommended in my last post?

Quote:

There's a problem here; your partitions seem to overlap. Partition 1 should start on cylinder 1 and end on cylinder 5737; partition 2 should start on cylinder 5738, not 5737, and so on.

(I realize that partitions can begin and end in the middle of a cylinder, but then why does the warning "Partition 2 does not end on cylinder boundary" only appear for partition 2?)

To make sure, let's see the partition limits in blocks, not in cylinders. Please do fdisk -lu /dev/sda and post the results.

Did you create the partitions yourself using fdisk, or did the installation program do it automatically?