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I want to install centOS 7 along side windows 8.1 for this I'm planning to do partition in a following way.

/boot - 500MB - Standard Partition
/swap - Half of my RAM size
/root - 20GB - Standard Partition
/home - Rest of my space - Standard Partition

The problem is: if I create /swap first, then I couldn't create Standard Partition anymore. Likewise if I create Standard first, I couldn't create /swap.

The error message is: Unable to allocate requested partition scheme.

After research, I understand that my MBR disk can not have more than 4 primary partition. Here is the current status of my disk

My Partition

As per as my understanding, Windows already took 3 primary partition

System (C)
System Reversed (E)
Extended Partition (container of Data and AOMEI Recovery Partition)

and CentOS require 2 more Primary Partition: one for /boot and one for the rest (correct me this part if I'm wrong)

Now I have no idea what I should do next to fix this problem. Should I change the setup of CentOS partition or do something to reduce the number of Primary Partitions on Windows and how to do this without losing data.

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    centos does not require any primary partitions. linux has no difficulty booting from extended partitions. – cas Jan 5 '18 at 6:32
  • if you want to avoid repartitioning that disk, your best bet is to just have a single partition with /, /boot, /home, and everything else on it (i.e. that 115GB unallocated partition), and use a swap file instead of a swap partition (or don't bother with swap at all). Alternatively, install Virtual Box and run Centos in a VM. Yet another alternative is to use LVM (centos installer should offer this automatically) and it will make LVM volumes as needed from that 115GB unallocated partition. – cas Jan 5 '18 at 6:36
  • When I try to set LVM volumes for all my disk, the installer said that "/boot can not be LVM". I don't remember the full sentence exactly. Are there any problems if I remove swap partition? Every tutorial I read on the Internet told me that swap is neccessary :( – Huy Jan 5 '18 at 8:24
  • does the centos installer give you the option of not having a /boot partition? e.g. "install on one big filesystem" or words to that effect? RE: swap - how much RAM do you have, and what do you expect to be using the system for? btw, you can always use a swapfile - they're a bit slower than using a swap partition, but it works. – cas Jan 5 '18 at 9:24
  • swap is useful but not absolutely necessary. running out of RAM is no different to running out of RAM+SWAP, it just happens a little sooner. – cas Jan 5 '18 at 9:25
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To circumvent the 4 primary partitions limit, you can create an extended partition in lieu of a primary partition, and then split it in four logical partitions (/, /boot, /swap, and /home).

Also, in the CentOS installer, choose the option to re-format these partitions (except the swap of course). It solved the problem for me when I had the same error message.

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Here is the way I solved this problem:

Move 115 GB unallocated (the one with black bar) into the Extended Partition. Then it would become freespace (with green bar). Now you can install CentOS on this free partition. I used EaseUS to move the partition.

Before partition format (not working):

System Reversed (E)
Unallocated Space
System (C)
Extended Partition (container of Data, AOMEI Recovery Partition)

Working partition format:

System Reversed (E)
System (C)
Extended Partition (container of Data, AOMEI Recovery Partition, Free space)

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