Apologies first of all. I'm a newbie, and I'm sure it will be obvious there are many things I don't understand.
I'd like to install both Ubuntu and CentOS on a new machine. Ubuntu is what I am used to and comfortable with (and what is currently connecting to the network in an unproblematic way), but for some software/work reasons I'd like the option of booting into CentOS.
Basic setup of the machine: two 2-terabyte hard drives, /dev/sda1, /dev/sda2
I installed CentOS first. Now I am trying to install Ubuntu. Ubuntu isn't seeing my CentOS installation. In order to not just write over CentOS, I went into the partition editor. But I don't know how to edit my partitions. I see that there's a /dev/sda1 on with 524 MB allocated to it, ext4 filesystem, 52 MB used. I presume that's where CentOS is installed. then I have 1999873 MB unallocated free space.
How do I set up /dev/sda so that Ubuntu installs nicely alongside CentOS? I assume I have to set up partitions in the unallocated free space. Do I set up another 524 MB partion, say its ext4, and say that the mount point (confused on this concept) is /boot? Then do I set up another partition with the rest of the space, with mount point / ? Do I set up my swap space at the end of /dev/sda as a last partition?
Thanks, and apologies for my ignorance. I have been trying to read about this online but it is hard to find discussions of the issues pitched to my level and it would be helpful to have a dialogue.
Thanks for all the responses. My question has now evolved. Before I knew that anyone had replied, I decided to install Ubuntu as the first OS, allowed it to wipe CentOS, then reinstalled CentOS, pointing it the same disk /dev/sda (thanks for the correction) as the Ubuntu installation. I installed grub and now I can boot into both OSs. So I'd be a happy clam if it weren't for Adaephon's comment below. According to what I can glean from looking at the display in gparted, when I installed Ubuntu from my Live CD, it took a 487 MB partition for /boot/efi and says it's using 3.04 MiB of space. I let CentOS make its own decisions,and it took 500 MB for its boot partion, after a 6.95 GB root partition. I don't know if that was enough space or whether I am going to have problems down the road. Definitely better to fix them now if so!
Here is the output of fdisk -l /dev/sda /dev/sdb (from Ubuntu):
Disk /dev/sda: 2000.4 GB, 2000398934016 bytes 255 heads, 63 sectors/track, 243201 cylinders, total 3907029168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes Disk identifier: 0x00000000 Device Boot Start End Blocks Id System /dev/sda1 1 3907029167 1953514583+ ee GPT Partition 1 does not start on physical sector boundary. Disk /dev/sdb: 2000.4 GB, 2000398934016 bytes 81 heads, 63 sectors/track, 765633 cylinders, total 3907029168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes Disk identifier: 0x000315ee Device Boot Start End Blocks Id System /dev/sdb1 2048 3907029167 1953513560 8e Linux LVM
Here is the output of df -l -xtmpfs -xdevtmpfs
Filesystem 1K-blocks Used Available Use% Mounted on /dev/sda2 7037432 3323776 3333088 50% / /dev/sda1 497696 2116 495580 1% /boot/efi
It seems it is an EFI machine.