Devices · Lesson 3 of 7
Device Names
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Linux device names reflect the kernel subsystem and driver presenting an interface, not always the physical connector printed on the hardware. Learn the common patterns, but discover the actual mapping on the current system before making storage changes.
SCSI-Layer Disk Names
Disks presented through the SCSI disk layer commonly use sd names. This includes many SCSI, SATA, USB-storage, and virtual disks:
/dev/sda: one whole disk/dev/sdb: another whole disk/dev/sda3: partition 3 on/dev/sda/dev/sdb1: partition 1 on/dev/sdb
Letters reflect enumeration, not a durable identity. Adding a controller, changing firmware order, or attaching a device can change which disk receives a particular letter.
CheckUnder the sd naming pattern, which path denotes partition 1 on /dev/sdb?
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Names That End in Digits
Some whole-device names already contain digits, so their partition names use p as a separator:
/dev/nvme0n1: NVMe namespace 1 on controller 0/dev/nvme0n1p2: partition 2 on that namespace/dev/mmcblk0: an MMC block device/dev/mmcblk0p1: partition 1 on that device
NVMe devices are not normally named /dev/sdX; they use the NVMe subsystem's naming convention.
CheckWhich path denotes partition 2 of /dev/nvme0n1?
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Logical and Virtual Block Devices
Linux also creates block devices that do not map one-to-one to a physical disk:
/dev/dm-Nfor device-mapper devices, often accompanied by descriptive links under/dev/mapper//dev/mdNfor Linux software RAID arrays/dev/loopNfor regular files attached as loop block devices
Partitions, encryption layers, RAID, logical volumes, and filesystems form a stack. Use tools such as lsblk to see parent-child relationships instead of inferring the stack from a name alone.
CheckWhich location commonly provides descriptive links for device-mapper devices?
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Persistent Storage Links
User-space device management creates links under /dev/disk/, commonly grouped as:
by-idfor hardware or transport identifiersby-uuidfor filesystem UUIDsby-labelfor filesystem labelsby-partuuidfor partition-table UUIDsby-pathfor topology-dependent paths
Choose an identifier that matches what must remain stable. A filesystem UUID identifies a filesystem, not necessarily the physical disk beneath it. Cloning a filesystem can duplicate its UUID, so verify uniqueness before relying on it.
CheckWhy are /dev/disk/by-id/ links often preferable to /dev/sdX in device-specific configuration?
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Pseudo-Device Names
Names such as /dev/null, /dev/zero, and /dev/urandom describe kernel pseudo-devices rather than physical storage. /dev/null discards writes and returns end-of-file on reads; /dev/zero supplies zero bytes; /dev/urandom supplies bytes from the kernel random-number generator.
CheckWhat does reading from /dev/zero produce?
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Use Explore Hardware Devices in Linux to compare names, persistent links, and lsblk relationships before attempting partition work.
Summary
You can now decode common Linux storage names without treating them as permanent identity.
- Read
sdXNUMBERas ansddisk partition. - Use
pNUMBERwhen the whole-device name already ends in a digit. - Recognize logical devices such as device mapper, RAID, and loop devices.
- Prefer persistent links chosen for the identity you need.
- Distinguish storage names from kernel pseudo-devices.
Practice
In the practice terminal, run: lsblk It should print a table or tree of block devices, each row showing NAME, SIZE, and TYPE.
lsblk shows the block device stack.
Lesson complete
You finished Device Names. Nice work — keep the momentum going.