Using the Linux lsscsi Command to View SCSI Devices

The lsscsi command is a dedicated Linux utility designed to scan the sysfs virtual file system and provide a clean, human-readable summary of all attached SCSI devices and their attributes. This article explains the primary purpose of the lsscsi command, how to interpret its default output, and how to utilize common flags to troubleshoot storage hardware, map device paths, and inspect storage transport protocols.

Purpose of the lsscsi Command

Modern Linux systems treat a wide range of storage interfaces—including traditional SCSI, SAS, SATA, USB storage, and Fibre Channel—as SCSI devices through the kernel's SCSI subsystem. The primary purpose of lsscsi is to translate the complex directory structure in /sys/bus/scsi/devices/ into a concise, organized list.

System administrators rely on lsscsi to quickly answer critical storage questions:

Which physical disk corresponds to which /dev/sd* device node?
What are the SCSI addresses (Host, Channel, Target, LUN) for connected drives?
Which storage vendor, model, and firmware revisions are active?
What transport layer (e.g., ATA, FC, SAS) connects the device to the host?

Reading the Default Output

Running the lsscsi command without additional arguments outputs one line per SCSI device. A typical output resembles the following:

[0:0:0:0]    disk    ATA      Crucial_CT500MX5 023   /dev/sda 
[1:0:0:0]    cd/dvd  PLDS     DVD-RW DH16AFSH  BL11  /dev/sr0 
[6:0:0:0]    disk    SanDisk  Ultra USB 3.0    1.00  /dev/sdb

The output consists of five primary columns:

SCSI Address (HCTL Tuple): The bracketed numbers [Host:Channel:Target:LUN] pinpoint the exact location in the SCSI hierarchy.
- Host: The host adapter (HBA) number.
- Channel: The bus channel on the controller.
- Target: The device ID assigned by the controller.
- LUN: The Logical Unit Number within the target.
Device Type: The SCSI peripheral device type, such as disk, cd/dvd, or tape.
Vendor: The manufacturer name reported by the device firmware.
Model and Revision: The product model string followed by the active firmware revision number.
Device Node: The Linux device path in the /dev filesystem used for mounting and partition management.

Essential Command Options

While the standard output is useful for basic inventory, lsscsi includes specific flags to display extended hardware details:

Show Device Capacities (-s): Appending -s displays the storage capacity of any detected disks alongside the device node.
```
lsscsi -s
```
Inspect Transport Protocols (-t): The -t flag exposes transport information, revealing target port identifiers, SAS addresses, or World Wide Names (WWNs) for Fibre Channel connections.
```
lsscsi -t
```
Display Generic SCSI Nodes (-g): Adding -g shows the associated /dev/sg* (SCSI Generic) device node, which is essential for issuing low-level SCSI commands via tools like sg3_utils or smartctl.
```
lsscsi -g
```
Detailed Sysfs Paths (-v or -vv): Verbose flags map each device directly to its corresponding directory in /sys, simplifying deep kernel-level troubleshooting.

Why Use lsscsi Over Alternative Commands

Commands like lsblk and fdisk -l excel at showing block layers, partition tables, and filesystem mount points. However, they abstract away much of the underlying SCSI topology. The lsscsi utility focuses entirely on the controller-to-device relationship, making it the most direct and efficient tool for diagnosing controller mapping issues, multipath configurations, and storage fabric connections.