sd0

sd0 is a device name used by several Unix-like operating systems to refer to the first SCSI disk device. The “sd” prefix stands for SCSI disk, and the trailing number denotes the unit or device number assigned by the kernel. In practice, software and administrators access the disk through device files such as /dev/sd0 or /dev/rsd0 for raw access.

Partitions on the disk are typically addressed by appending a partition letter, for example /dev/sd0a, /dev/sd0b, with the full disk sometimes represented as /dev/sd0c on some systems. The exact naming and partition scheme can vary by OS and version, but the general convention is that sd0 identifies the first SCSI disk in the system.

Context and variations: On many Linux systems, the equivalent first disk is named /dev/sda (SATA or SCSI), rather than sd0. BSD variants continue to use the sd0 naming for the first SCSI disk, with additional disks named sd1, sd2, and so on. Other storage interfaces have different conventions—e.g., newer FreeBSD naming for certain drives may use adaX for SATA drives, and NVMe devices use names like nvme0n1—so sd0 specifically refers to a SCSI disk in the naming scheme.

History and usage: The sd naming convention originated in BSD Unix as a standardized way to refer to SCSI disks across different hardware platforms. It remains in use in FreeBSD, NetBSD, and OpenBSD for SCSI disks, though modern systems increasingly incorporate other device naming schemes as storage technologies evolve.