In the previous chapter, we looked at installing CentOS 9 on the same disk as Windows. This so-called “dual boot” configuration allows the user to have both operating systems installed on a single disk drive with the option to boot one or the other when the system is powered on. This chapter is intended for users who have decided they like CentOS 9 enough to delete Windows entirely from the disk and use the resulting space for Linux. In the following sections, we will work through this process step by step.

Unmounting the Windows Partition

If the steps in the Dual Booting CentOS Stream with Windows chapter were followed to mount the Windows partition from within CentOS 9, steps should be taken to unmount the partition before continuing with this chapter. For example, assuming that the Windows partition was mounted as /mnt/ windows, it can be unmounted as follows:

# umount /mnt/windowsCode language: Shell Session (shell)

The /etc/fstab file should also be edited to remove the /mnt/windows auto-mount if it was previously added.

Deleting the Windows Partitions from the Disk

The first step in freeing up the Windows partition for use by CentOS is to delete that partition. Before doing so, however, any data you need to keep must be backed up from both the Windows and partitions. Having done that, it is safe to proceed with this chapter.

To remove the Windows partitions, we first need to identify the disk on which they reside using the fdisk tool:

# fdisk -l
Disk /dev/nvme0n1: 64 GiB, 68719476736 bytes, 134217728 sectors
Disk model: VMware Virtual NVMe Disk
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 7A38CD86-091E-4781-BFB0-928FD383C935

Device             Start       End  Sectors  Size Type
/dev/nvme0n1p1      2048    206847   204800  100M EFI System
/dev/nvme0n1p2    206848    239615    32768   16M Microsoft reserved
/dev/nvme0n1p3    239616  49362943 49123328 23.4G Microsoft basic data
/dev/nvme0n1p4 132933632 134213631  1280000  625M Windows recovery environment
/dev/nvme0n1p5  49362944  51460095  2097152    1G Linux filesystem
/dev/nvme0n1p6  51460096 132933631 81473536 38.8G Linux LVMCode language: plaintext (plaintext)

In the above example output, the system contains one physical disk drive referenced by device name /dev/nvme0n1. On that disk drive are six partitions accessed via the device names /dev/ nvme0n1p1 through /dev/nvme0n1p6, respectively. Based on the values in the Types column, three Windows-related partitions exist. The first is the Windows system partition, while the second, much larger, partition is the Windows boot partition containing the Windows operating system and user data, followed by the Windows recovery partition.

To remove the partitions, start the fdisk tool using the device name of the disk containing the partition (/dev/nvme0n1 in this instance) and follow the instructions to display the partition and sector information once again:

# fdisk /dev/nvme0n1

Welcome to fdisk (util-linux 2.37.4).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Command (m for help): p

Disk /dev/nvme0n1: 64 GiB, 68719476736 bytes, 134217728 sectors
Disk model: VMware Virtual NVMe Disk
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 7A38CD86-091E-4781-BFB0-928FD383C935

Device             Start       End  Sectors  Size Type
/dev/nvme0n1p1      2048    206847   204800  100M EFI System
/dev/nvme0n1p2    206848    239615    32768   16M Microsoft reserved
/dev/nvme0n1p3    239616  49362943 49123328 23.4G Microsoft basic data
/dev/nvme0n1p4 132933632 134213631  1280000  625M Windows recovery environment
/dev/nvme0n1p5  49362944  51460095  2097152    1G Linux filesystem
/dev/nvme0n1p6  51460096 132933631 81473536 38.8G Linux LVM

Partition table entries are not in disk order.

Command (m for help):Code language: plaintext (plaintext)

Before proceeding, note the start and end addresses of the partitions we will delete (in other words, the start of /dev/nvme0n1p2 and the sector before the start of /dev/nvme0n1p5).

At the command prompt, delete the Windows partitions (these being partitions 2, 3, and 4 on our example system):

Command (m for help): d
Partition number (1-6, default 6): 2

Partition 2 has been deleted.

Command (m for help): d
Partition number (1,3-6, default 6): 3

Partition 3 has been deleted.

Command (m for help): d
Partition number (1,4-6, default 6): 4

Partition 4 has been deleted.Code language: plaintext (plaintext)

Now that we have deleted the Windows partitions, we need to create the new CentOS partition in the vacated disk space. The partition number must match the number of the first partition removed (in this case, 2). It will also be necessary to enter the Start and End sectors of the partition precisely as reported for the old partition (fdisk will typically offer the correct values by default, though it is wise to double-check). If you are prompted to remove the NTFS signature, enter Y:

Command (m for help): n
Partition number (2-4,7-128, default 2): 2
First sector (206848-134217694, default 206848): 
Last sector, +/-sectors or +/-size{K,M,G,T,P} (206848-49362943, default 49362943): 

Created a new partition 2 of type 'Linux filesystem' and of size 23.4 GiB.
Command (m for help): Code language: plaintext (plaintext)

Having made these changes, the next step is to check that the settings are correct:

Command (m for help): p
Disk /dev/nvme0n1: 64 GiB, 68719476736 bytes, 134217728 sectors
Disk model: VMware Virtual NVMe Disk
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 7A38CD86-091E-4781-BFB0-928FD383C935

Device            Start       End  Sectors  Size Type
/dev/nvme0n1p1     2048    206847   204800  100M EFI System
/dev/nvme0n1p2   206848  49362943 49156096 23.4G Linux filesystem
/dev/nvme0n1p5 49362944  51460095  2097152    1G Linux filesystem
/dev/nvme0n1p6 51460096 132933631 81473536 38.8G Linux LVM
Code language: plaintext (plaintext)

To commit the changes, we now need to write the new partition information to disk and quit from the fdisk tool:

Command (m for help): w
The partition table has been altered.
Syncing disks.Code language: plaintext (plaintext)

Formatting the Unallocated Disk Partition

To make the new partition suitable for use by CentOS 9, it needs to have a file system created on it. The recommended file system type for the current release of CentOS is XFS which will be covered in greater detail in the chapter entitled Adding a New Disk Drive to a CentOS Stream 9 System. Creation of the file system is performed using the mkfs.xfs command as follows:

# mkfs.xfs -f /dev/nvme0n1p2
meta-data=/dev/nvme0n1p2         isize=512    agcount=4, agsize=1536128 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=1        finobt=1, sparse=1, rmapbt=0
         =                       reflink=1    bigtime=1 inobtcount=1
data     =                       bsize=4096   blocks=6144512, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
log      =internal log           bsize=4096   blocks=3000, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0Code language: plaintext (plaintext)

Mounting the New Partition

Next, we need to mount the new partition. In this example, we will mount it in a directory named /data. You are free, however, to mount the new partition using any valid mount point you desire or to use it as part of a logical volume (details of which are covered in the chapter entitled Adding a New Disk to a CentOS Stream 9 Volume Group and Logical Volume). First, we need to create the directory to act as the mount point:

# mkdir /dataCode language: plaintext (plaintext)

Secondly, we need to edit the mount table in /etc/fstab so that the partition is automatically mounted each time the system starts. At the bottom of the /etc/fstab file, add the following line to mount the new partition (modifying the /dev/nvme0n1p2 device to match your environment):

/dev/nvme0n1p2    /data   xfs defaults 0 0Code language: plaintext (plaintext)

Finally, we can manually mount the new partition (note that this will not be necessary on subsequent reboots as the partition will automount due to the setting we added to the /etc/fstab file above):

# mount /dataCode language: PHP (php)

To check the partition, run the following command to display the available space:

# df -h /data
Filesystem      Size  Used Avail Use% Mounted on
/dev/nvme0n1p2   24G  200M   24G   1% /data
Code language: plaintext (plaintext)

Summary

The Windows partitions in a dual boot configuration can be removed anytime to free up space for a CentOS system by identifying which partitions belong to Windows and then deleting them. Once deleted, the unallocated space can be used to create a new filesystem and mounted to make it available to the CentOS system.