How to Create a Partition

Hard drive partitions allow the computer to treat one hard drive as multiple distinct volumes. This enables you to install multiple operating systems or create a second drive for storing specific files. You can easily create new partitions from your free space in Windows and Mac, though Windows XP users will need third-party tools to accomplish the same thing.

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Method 1 of 5: Creating a Partition in Windows Vista, 7, and 8

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   Open the Disk Management utility. Open the Run dialog box from the Start menu or by pressing ⊞ Win+R. Type diskmgmt.msc and press ↵ Enter. This will open a window that allows you to manage all of the volumes and drives installed in your system.^[1]
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   Manage your unallocated space. Partitions are created from unallocated space or free space on your hard drive. You can create more unallocated space by shrinking an existing volume. This will remove the available storage space from that volume and turn it into unallocated space.

   • Right-click a volume and select "Shrink Volume..." to begin the volume shrinking process. You will be able to choose how much of the free space you want to remove from the volume to turn into unallocated space.
   • You won't be able to turn all of the available storage into unallocated space because some of that available storage is reserved for unmovable files. You can increase the space you can reclaim by defragmenting the drive first.
   • If you want to merge two blocks of unallocated space together, you will need to use a tool like GParted or Partition Manager.
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   Create the new partition. Right-click on the unallocated space and select "New Simple Volume". This will open a wizard that will walk you through the steps to create the new partition.

   • Set the size. The first thing you will be asked is how big you want the partition to be. By default, it will be set to the same size as the entire block of unallocated space, but you can choose to make it smaller if you wish. Any unused space will remain unallocated.
   • Assign a drive letter. All partitions need a drive letter, which allows them to have addresses for files located on the partition. You can choose any letter that you'd like as long as you don't already have a drive using that letter. Avoid using A:and B: as these are older drive letters reserved for floppy disk drives.
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   Format the volume. Ensure that the volume is set to be formatted, otherwise you cannot use it to store files. If you are using the volume to store files for Windows, set the file system to NTFS. Enter a name for the volume in the "Volume label" field.^[2]

   • Check the "Perform a quick format" box unless you are worried that the disk is damaged.
   • If you are going to be using the volume to install an operating system on, you don't have to worry about formatting it now.
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Method 2 of 5: Creating a Partition in OS X

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   Open the Disk Utility program. You can access Disk Utility from the Utilities folder in the Applications folder. Disk Utility comes installed on every Mac.

   • Note: This method only works on OS X 10.5 (Leopard) and above. Users of older versions will need to use partition software to create a new partition from an existing one.
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   Select your hard drive. In the left frame, select the hard drive that you want to create a partition on. Click the "Partition" tab to view the partitions on the drive. You will see all of the current partitions on that drive laid out in the right side of the window. Used space is represented as light blue, while free space is represented as white.
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   Shrink the existing partition. Select the partition you want to shrink and then either enter in the new size you want into the field or click and drag the bottom-right corner of the partition block. Click Apply and then Partition to save the changes.

   • You won't be able to shrink it into the blue area, as this represents files that exist on the original partition.
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   Create a new partition. After resizing your original partition, click the "+" button at the bottom of the Partition Layout window. A new partition will be created out of the available space left after shrinking the original and added to the partition layout.
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   Change the size of the partition. By default, the new partition will take up all the available space left over after resizing. You can adjust the size of the partitions by using the slider between the two in the Partition Layout window. You can also select a partition and enter the size you want it to be in the "Size" field.
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   Select a file format. The original partition will keep its old file system, but you will need to format the newly created partition in order to start storing files on it. Choose "Mac OS Extended (Journaled)" from the Format drop-down menu.

   • If you're creating a partition to install Windows on, leave it unformatted for now. The Windows installer will format it to the correct file system.
   • Give the new partition a name so that you can easily identify what's on it.
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   Apply your changes. Click the Apply button, and then click Partition to accept your changes and create the new partition. You can now use your new partition just like you would any hard drive.^[3]
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Method 3 of 5: Creating a Partition in Windows XP

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   Download a partition tool. There is no way to shrink a volume in Windows XP, which means that you can't create a partition out of the free space on your hard drive. You will need to use a partition utility like Partition Wizard or GParted to shrink your existing volume.^[4]
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   Resize your existing partition. Use the partition tool you downloaded to resize one of your existing partitions. The amount you can shrink the partition is based on the location of unmovable files, and this amount can be increased by defragmenting your hard drive.

   • See this guide for details on using GParted to change your partition size.
   • See this guide for details on using Partition Manager to change your partition size.
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   Create a new partition. Once you've resized your old partition, you will have a chunk of unallocated space. You can use this to create your new partition. You can either use all of the available unallocated space or you can set it to a portion of it.

   • You can either create the partition using the partition tool that you downloaded, or you can use Windows Disk Management as described in the first section.
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   Format the new partition. Before you can use your new partition, you will need to give it a file system and a label.
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   Repair your boot record. If you resized your operating system's partition, it could cause Windows to not be able to boot. In order to fix this you will need to perform a repair installation of Windows. You will need the Windows XP installation disc for this process.

   • See this guide for detailed instructions on repairing your Windows XP installation.
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Method 4 of 5: Formating a Partition in Linux using the CLI

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   First unmount the partition that you would like to format. Assuming that /dev/sdax is the partition that you want to format, run the following command to unmount it.
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sudo umount /dev/sdax

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   • Note You cannot unmount the root partition while the system is running.Use a live cd or live usb to format the root partition. /dev/sdax must be replaced by the appropriate partition name. Use sudo fdisk -l to get the list of partitions on your system. For instance, to format /dev/sb2, use sdb2 in place of sdax.
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   To format the partition that you unmounted, simply run the command,
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sudo mkfs.ext4 /dev/dev/sdax This will create an ext4 filesystem on /dev/sdax. Please note that this will erase all data on the partition.

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   • Note Linux supports several filesystems. You may use btrfs, xfs or even reiserfs.
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Method 5 of 5: Creating a Partition in Linux using the CLI

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   Using fdisk

   • To get a list of the disks attached to your computer and the partitions on them, run sudo fdisk -l.
   • To get the list of partitions on /dev/sdb, run sudo fdisk /dev/sdb -l.
   • To create a partition on the disk /dev/sdb, first run the command sudo fdisk /dev/sdb.
   • After you type in your password and press enter, you will get a prompt like the one in the image below.
     
   • Type in n.
   • You will be prompted to select the partition type. Enter p for creating a primary partition and e for creating an extended partition.
   • Next you will be prompted to select the partition number, first sector and last sector. Just press enter and go with the default choice.
     
   • You have successfully created a new partition.
   • To create a new partition, there must be enough free space on the disk. To shrink the first partition on the disk /dev/sda by 200MB, use the command sudo resize2fs /dev/sda1 200M. Replace M by G to specify size in gigabytes.