whatis block-device
Block Device
A device such as a disk, partition, or USB drive that is read and written in fixed-size blocks, listed by lsblk.
What Is a Block Device in Linux?
Block devices appear under /dev with names like sda, nvme0n1, mmcblk0, and dm-0. The kernel caches them in memory and schedules their I/O, unlike character devices which stream bytes.
Layers stack on top of one another: a physical disk holds partitions, a partition can hold a LUKS container, which can hold LVM volumes, each of which is itself a block device.
Example
lsblk -o NAME,SIZE,TYPE,FSTYPE,MOUNTPOINTSLearn more about Block Device
- The /dev Directory Explained: Device Files, null, zero and random Everything in /dev is a file that is not a file. Block versus character devices, why /dev/null and /dev/zero differ, what /dev/random actually blocks on now, and why the directory is rebuilt from nothing on every boot.
- Linux I/O Schedulers: mq-deadline, BFQ, Kyber, and none The scheduler decides the order requests reach your disk. On spinning rust it matters enormously, on NVMe it often should be switched off, and the right default differs per device.
- The dd Command Explained dd copies raw data block by block, which makes it the standard tool for writing bootable USB drives, cloning disks, and wiping data securely. It is also famous for having no confirmation prompt, this guide covers safe usage and why it earned the nickname "disk destroyer."
Related tools
- dd Bootable USB Builder Write an ISO to a USB drive, with the device identification and checksum checks to run first.