i want to triple boot my system with debian ubuntu and windows xp. i already have uuntu and windows xp and i want to install debian without getting ubuntu effected. what is the selection of the root criteria as presently dev/sda7 but i have free space and while trying to install debian the root moutn point is being set to this free space. is thia going to cause problem and if yes how should i install debian. Thank You

I'm not sure what you mean by "Free Space".

Free space does not have a /dev/sda associated with it. ie free space is not partitioned. Is this what you have? If yes, then create a partition, big enough for Debain, and do your install. I would suggest you make a partition for /home as well. Don't try to use the same /home as Ubuntu, you will cause application problems.

What is on /dev/sda7 now?

i aplogize for putting my question in a cryptic fashion. i'm trying to build the LFS system someone on this forum suggested me to use debian since ubuntu had problems regarding glibc. for what i'm worried for the istallation of a new os is that some time back i was trying to install fedora with ubuntu and windows already present and i dnt what caused up an error tha none of the linux system were recoverable with the eror reading unable to find root partition. now at present while installing ubuntu i had given 4.1 GB swap space, 10GB ext4 partition mounted at /, and 85 GB ext4 partition mounted at /home. Now i have a 41 GB ext 3 file system for LFS partition and 49 GB free space which i would like to use to istall for debian. my windows partition uses 54 GB file system. while trying to istall debian the 49 GB free space was mounted at /; so my question is will there be any error so as to the 10GB axt4 partition which was mounted at / as there were no mount point seen with the other two ext4 partition.
After running sudo fdisk -l the following is the output

Disk /dev/sda: 320.1 GB, 320072933376 bytes
255 heads, 63 sectors/track, 38913 cylinders, total 625142448 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xa42d04a3

Device Boot Start End Blocks Id System
/dev/sda1 63 257039 128488+ de Dell Utility
/dev/sda2 * 257040 105113294 52428127+ 7 HPFS/NTFS/exFAT
/dev/sda3 105113356 604669951 249778298 5 Extended
/dev/sda4 604670535 625137344 10233405 db CP/M / CTOS / ...
/dev/sda5 105113358 234147374 64517008+ 7 HPFS/NTFS/exFAT
/dev/sda6 234147840 242147327 3999744 82 Linux swap / Solaris
/dev/sda7 242149376 262148095 9999360 83 Linux
/dev/sda8 262150144 428888063 83368960 83 Linux
/dev/sda9 428890112 507992063 39550976 b W95 FAT32
ankit@ankit-Inspiron-1012:~$

i have attached the screenshot of the disks partitioning as given by disk utility
Thank You

Attached Thumbnails

 

I think much of the problem here is you do not understand what happens ( big picture ) when you boot a linux system. I'm guessing you are using grub2, since that is the default boot loader installed with Ubuntu. Since your system was booting windoze and Ubuntu without problems.

O.K. so after POST finishes, ( that is a BIOS hardware function ), the bios code reads the MBR ( Master Boot Record ). That code sends the disk to read the boot loader ( Grub2 ). Depending on user input, Grub2 will send the disk hardware off to read and start loading the OS of the users choice.

Now for linux, you have to specify what partition the system ( the /boot directory ) is on. The kernel is loaded and takes over the boot process. For linux, it will find the file called /etc/fstab. This file controls what partitions are mounted. If a partition is not mounted, it is never read, or written to by the system. You have an /etc/fstab file for each system you install.

If you install a new system on the 49 gig partition, you control during the install what partitions will be added to /etc/fstab. You specify this by putting the root partition on
/dev/sda10 ( that is your free space ). If you do not put /home on its own partition, then it will be created on the same partition as the / ( root ) file system. That is O.K. it will work.

There is no reason to believe this will cause any issue with your Ubuntu system, or what ever you put on the 41 gig partition ( LFS ? ).

One thing you have to be careful of is NOT to install another boot loader to the MBR. After your Debain install is finished, there will not be an entry to boot Debain in Grub2. You will need to boot the system you installed the Grub2 with, and add the entry in Grub2 with that system.

There are How To tutorials on many boards on how to edit grub2 files and add an OS.

If you were to install another boot loader to the MBR with your Debain install, then other OS's won't boot.

So, the simple answer to your question is, the new system will not affect any other installed system.

Ubuntu's problems with glibc are maily becaue it comes form Debian's unstable branch and is therefor... Unstable.