Access the contents of a file system by mounting it on an empty directory. This directory is called a mount point. When the directory is mounted, use the ls command to list its contents. Many file systems are automatically mounted when the system boots.

A mount point differs slightly from a Microsoft Windows drive letter, where each file system is a separate entity. Mount points enable multiple file system devices to be available in a single tree structure. This mount point is similar to NTFS mounted folders in Microsoft Windows.

A block device is a file that provides low-level access to storage devices. A block device must be optionally partitioned, and a file system that was created before the device can be mounted.

The /dev directory stores block device files, which RHEL creates automatically for all devices. In RHEL 9, the first detected SATA, SAS, SCSI, or USB hard drive is called the /dev/sda device; the second is the /dev/sdb device; and so on. These names represent the entire hard drive.

Usually, the entire storage device is not created into one file system. To create a partition, divide the storage devices into smaller chunks.

With partitions, you can compartmentalize a disk: the various partitions might be formatted with different file systems or be used for other purposes. For example, one partition might contain user home directories, whereas another partition might contain system data and logs. Even when the home directory partition is loaded with data, the system partition might still have available space.

Partitions are block devices in their own right. For example, on the first SATA-attached storage, the first partition is the /dev/sda1 disk. The second partition of the same storage is the /dev/sda2 disk. The third partition on the third SATA-attached storage device is the /dev/sdc3 disk, and so on. Paravirtualized storage devices have a similar naming system. For example, the first partition on the first storage device is the /dev/vda1 disk. The second partition of the second storage device is the /dev/vdb2 disk, and so on.

An NVMe-attached SSD device names its partitions differently from a SATA-attached device. For NVMe storage devices, the nvmeX part of the name refers to the device; the nY part refers to the namespace; and the pZ part refers to the partition. For example, the first partition for the first namespace on the first disk is the /dev/nvme0n1p1 partition. The third partition for the first namespace on the second disk is the /dev/nvme1n1p3 partition, and so on.

SD or MMC cards can sometimes have a similar naming system to the SATA devices (/dev/sdN). In some cases, SD or MMC cards might have names such as /dev/mmcblk0p1, where the mmcblkX part of the name refers to the storage device, and the pY part of the name refers to the partition number on that device.

An extended listing of the /dev/sda1 device file on the host machine reveals the b file type, which stands for a block device:

[user@host ~]$ ls -l /dev/sda1
brw-rw----. 1 root disk 8, 1 Feb 22 08:00 /dev/sda1

Another way of organizing disks and partitions is with Logical Volume Management (LVM). With LVM, it is possible to aggregate block devices into a volume group. Disk space in the volume group is separated into logical volumes, which are the functional equivalent of a partition on a physical disk.

The LVM system assigns names to volume groups and logical volumes on their creation. LVM creates a directory in the /dev directory that matches the group name, and creates a symbolic link within that new directory with the same name as the logical volume. That logical volume file is then available to be mounted. For example, when a myvg volume group and the mylv logical volume are present, the full path to the logical volume is the /dev/myvg/mylv file.