Device file
From Wikipedia:
- 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
Block devices provide buffered access to hardware devices and allow reading and writing blocks of any size and alignment.
The beginning of the device name specifies the type of block device. Most modern storage devices (e.g. hard disks, SSDs and USB flash drives) are recognised as SCSI disks (sd
). The type is followed by a lower-case letter starting from a
for the first device (sda
), b
for the second device (sdb
), and so on. Existing partitions on each device will be listed with a number starting from 1
for the first partition (sda1
), 2
for the second (sda2
), and so on. Other common block device types include for example mmcblk
for memory cards and nvme
for NVMe devices.
See also Persistent block device naming.
lsblk
The util-linux package provides the lsblk(8) 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 (sda1
to sda3
), each with a different file system.
wipefs
wipefs can list or erase file system, RAID or partition-table signatures (magic strings) from the specified device to make the signatures invisible for libblkid(3). It does not erase the file systems themselves nor any other data from the device.
See wipefs(8) for 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
Pseudo-devices
Device nodes that do not have a physical device.
- /dev/random, see random(4)
- /dev/shm
- /dev/null, /dev/zero, see null(4)
- /dev/full, see full(4)
- /dev/ttyX, where X is a number