- Device Naming
- Linux device naming
- Windows device naming
- FreeBSD device naming
- Solaris device naming
Device naming of storage devices varies from between operating systems
and sometimes between different releases of the same operating system.
This page attempts to cover the device naming conventions for various
storage related packages written by this author. Some of these packages
are Linux specific, while others were originally written for Linux then
ported to various other operating systems.
The overall device naming philosophy is to follow the device naming
conventions of each operating system, rather than attempt to follow a
"one naming convention fits all" approach. There is a section below for
each supported operating system. Since most of the examples on the
utility web pages
and the man pages are for Linux, some familiarity with Linux storage
device naming conventions may help users of other ports.
Linux device naming
Normal disk block devices have names like /dev/sda, /dev/sdb, /dev/sdc,
etc. SCSI disks in Linux have always had names like that but in recent
Linux kernels (e.g. lk 2.6 series) it is becoming more common for
almost all disks to be named like that. Partitions within a disk are
specified by a number appended to the device name, starting at 1 (e.g.
Tape drives are named /dev/st<num>
<num> starts at zero. Additionally one letter from this list:
"lma" may be appended to the name. CD, DVD and BD readers (and writers)
are named /dev/sr<num>
where <num> start at zero. There are
less used SCSI device type names, the dmesg and the lsscsi commands may
help to find if any are attached to
a running system.
There is also a SCSI device driver which offers alternate generic
access to SCSI devices. It uses names of the form /dev/sg<num>
where <num> starts at zero. The lsscsi
-g command may be useful
in finding these and which generic name corresponds to a device type
name (e.g. /dev/sg2 may
correspond to /dev/sda). In the lk 2.6 series a
block SCSI generic driver was introduced and its names are of the form
where h, c, t and l are numbers. Again see the
lsscsi command to find the correspondence between that SCSI tuple (i.e.
<h:c:t:l>) and alternate device names.
Prior to the Linux kernel 2.6 series these utilities could only use
generic device names (e.g.
/dev/sg1 ). In almost all cases in the Linux
kernel 2.6 series, any device name can be used by these utilities.
Windows device naming
Storage and related devices can have several device names in Windows.
Probably the most common in the volume name (e.g. D: ). There are also
a "class" device names such as PhysicalDrive<n>,
CDROM<n> and TAPE<n>. <n> is an
at 0 allocated in ascending order as devices are discovered (and
Some storage devices have a SCSI lower level device name which starts
with a SCSI (pseudo) adapter name of the form SCSI<n>: . To this
is added sub-addressing in the form of a "bus" number, a "target"
identifier and a "lun" (logical unit number). The "bus" number is also
known as a "PathId". These are assembled to form a device name of the
trailing ",<lun>" may be omitted in which case a lun of zero is
assumed. This lower level device name cannot often be used directly
since Windows blocks attempts to use it if a class driver has "claimed"
the device. There are SCSI device types (e.g. Automation/Drive
interface type) for which there is no class driver. At least two
transports ("bus types" in Windows jargon): USB and IEEE 1394 do not
have a "scsi" device names of this form.
In keeping with DOS file system conventions, the various device names
can be given in upper, lower or mixed case. Since PhysicalDrive<n> is
tedious to write, a shortened form of PD<n> is permitted by all
A single device (e.g. a disk) can have many device names. For example: PD0 can also be C: , D: and SCSI0:0,1,0 . The two volume
reflect that the disk has two partitions on it. Disk partitions that
are not recognised by Windows are not usually given a volume name.
However Vista does show a volume name for a disk which has no
partitions recognised by it and when selected invites the user to
format it (which may be rather unfriendly to other OSes).
These utilities assume a given device name is in the Win32 device
namespace. To make that explicit "\\.\" can be prepended to the device
names mentioned in this section. Beware that backslash is an escape
character in Unix like shells and the C programming language. In a
shell like Msys (from MinGW) each backslash may need to be typed twice.
The sg_scan utility in the
sg3_utils package lists out Windows device
names in forms that are suitable for other utilities to use. Note that
Windows operating systems prior to Windows 2000 are not supported.
FreeBSD device naming
SCSI disks have block names of the form /dev/da<num> where
<num> is an integer starting at zero. The "da" is replaced by
"sa" for SCSI tape drives and "cd" for SCSI CD/DVD/BD drives. Each SCSI
device has a corresponding pass-through device name of the form
<num> is an integer starting at zero.
The camcontrol devlist command
may be useful for finding out which
SCSI device names are available and the correspondence between between
class and pass-through names.
Solaris device naming
SCSI device names below the /dev
directory have a form like: c5t4d3s2
where the number following "c" is the controller (HBA) number, the
number following "t" is the target number (from the SCSI parallel
interface days) and the number following "d" is the LUN. Following the
"s" is the slice number which is related to a partition and by
convention "s2" is the whole disk.
OpenSolaris also has a c5t4d3p2
form where the number following the "p"
is the partition number apart from "p0" which is the whole disk. So a
whole disk may be referred to as either c5t4d3, c5t4d3s2 or c5t4d3p0 .
See this page
for more information.
And these device names are duplicated in the /dev/dsk and /dev/rdsk
directories. The former is the block device name and the latter is for
"raw" (or char device) access which is what sg3_utils needs. So in
OpenSolaris something of the form 'sg_inq
work. If it doesn't work then add a '-vvv' option for more debug
information. Trying this form 'sg_inq
/dev/dsk/c5t4d3p0' (note "rdsk"
changed to "dsk") will result in an "inappropriate ioctl for device"
The device names within the /dev
directory are typically symbolic links
to much longer topological names in the /device directory. In Solaris
cd/dvd/bd drives seem to be treated as disks and so are found in the
/dev/rdsk directory. Tape
drives appear in the /dev/rmt
There is also a sgen (SCSI generic) driver which by default does not
attach to any device. See the /kernel/drv/sgen.conf
file to control
what is attached. Any attached device will have a device name of the
form /dev/scsi/c5t4d3 .
Listing available SCSI devices in Solaris seems to be a challenge. "Use
the format command" advice
works but seems a very dangerous way to
list devices. [It does prompt again before doing any damage.] devfsadm
-Cv cleans out the clutter in the /dev/rdsk directory, only
what is "live". The cfgadm -v
command looks promising.
Some examples of storage device names of the supported operating
Table 1. Device naming
|hard disk partition
Some operating systems allow SCSI commands to be sent directly to class
device names using a pass-through interface. In Linux this is the case
in the lk 2.6 series.
Please send corrections and clarifications to the author.
Doug Gilbert (firstname.lastname@example.org)
Last updated: 4th February 2012