- In Unix-like operating systems, a device file or special file is an interface to a device driver that appears in a file system as if it were an ordinary file.
On Linux they are in the
/dev directory, according to the Filesystem Hierarchy Standard.
On Arch Linux the device nodes are managed by udev.
Block devices provide buffered access to hardware devices and allow reading and writing blocks of any size and alignment.
Block device names
The beginning of the device name specifies the kernel's used driver subsystem to operate the block device.
Storage devices, like hard disks, SSDs and flash drives, that support the SCSI command (SCSI, SAS, UASP), ATA (PATA, SATA) or USB mass storage connection are handled by the kernel's SCSI driver subsystem. They all share the same naming scheme.
The name of these devices starts with
sd. It is then followed by a lower-case letter starting from
a for the first discovered device (
b for the second discovered device (
sdb), and so on. Existing partitions on each device will be listed with the number that is assigned to them in the partition table, e.g.
sda1 for the partition
sda2 for partition
2, and so on.
a, the first discovered device.
e, the fifth discovered device.
The name of storage devices, like SSDs, that are attached via NVM Express (NVMe) starts with
nvme. It is then followed by a number starting from
0 for the device controller,
nvme0 for the first discovered NVMe controller,
nvme1 for the second, and so on. Next is the letter "n" and a number starting from
1 expressing the device on a controller, i.e.
nvme0n1 for first discovered device on first discovered controller,
nvme0n2 for second discovered device on first discovered controller, and so on. Existing partitions on each device will be listed with the letter "p" and the number that is assigned to them in the partition table. For example,
nvme0n1p1 for the partition with number
1 on first discovered device on first discovered controller,
nvme0n1p2 for partition
2, and so on.
0, the first discovered device on the first discovered controller.
2, the fifth discovered device on the third discovered controller.
SD cards, MMC cards and eMMC storage devices are handled by the kernel's
mmc driver and name of those devices start with
mmcblk. It is then followed by a number starting from
0 for the device, i.e.
mmcblk0 for first discovered device,
mmcblk1 for second discovered device and so on. Existing partitions on each device will be listed with the letter "p" and the number that is assigned to them in the partition table. The partition with number
1 in the partition table would be
mmcblk0p1, partition with number
2 would be
mmcblk0p2, and so on.
0, the first discovered device.
4, the fifth discovered device.
SCSI optical disc drive
The name of optical disc drives (ODDs), that are attached using one of the interfaces supported by the SCSI driver subsystem, start with
sr. The name is then followed by a number starting from
0 for the device, ie.
sr0 for the first discovered device,
sr1 for the second discovered device, and so on.
Udev also provides
/dev/cdrom that is a symbolic link to
/dev/sr0. The name will always be
cdrom regardless of the drive's supported disc types or the inserted media.
/dev/sr0- optical disc drive
0, the first discovered optical disc drive.
/dev/sr4- optical disc drive
4, the fifth discovered optical disc drive.
/dev/cdrom- a symbolic link to
Thepackage provides the utility which lists block devices, for example:
$ lsblk -f
NAME FSTYPE LABEL UUID MOUNTPOINT sda ├─sda1 vfat C4DA-2C4D /boot ├─sda2 swap 5b1564b2-2e2c-452c-bcfa-d1f572ae99f2 [SWAP] └─sda3 ext4 56adc99b-a61e-46af-aab7-a6d07e504652 /
In the example above, only one device is available (
sda), and that device has three partitions (
sda3), each with a different file system.
wipefs can list or erase file system, RAID or partition-table signatures (magic strings) from the specified device to make the signatures invisible for . It does not erase the file systems themselves nor any other data from the device.
Seefor more information.
For example, to erase all signatures from the device
/dev/sdb and create a signature backup
~/wipefs-sdb-offset.bak file for each signature:
# wipefs --all --backup /dev/sdb
Device nodes that do not have a physical device.