Master lsscsi: Understand SCSI, Storage Interfaces, and Linux Commands

What is SCSI?

SCSI (Small Computer System Interface) is a complete data‑transfer protocol that enables hosts to communicate with storage devices, transmitting commands, status, and block data. It sits between the operating system and external resources, and its functionality is typically embedded in device drivers or host adapters.

Common Hard‑Disk Interfaces

1. IDE Interface

IDE (Integrated Drive Electronics) integrates the drive controller with the disk, originally referring to ATA‑1 drives. It is inexpensive, highly compatible, but offers slower data transfer and no hot‑plug support.

2. SCSI Interface

SCSI is a high‑speed data‑transfer technology used mainly in servers and workstations. It supports multiple devices, hot‑plug, and offers high bandwidth, though at a higher cost.

3. SATA Interface

SATA (Serial Advanced Technology Attachment) uses serial communication with embedded clock signals, providing stronger error correction, hot‑plug capability, and is the prevailing interface for modern PCs.

lsscsi Command

lsscsi lists SCSI/SATA devices such as hard‑disk and optical drives.

Installation

# Debian/Ubuntu/Kali
apt-get install lsscsi
# Alpine
apk add lsscsi
# Arch Linux
pacman -S lsscsi
# CentOS
yum install lsscsi
# Fedora
dnf install lsscsi
# Docker
docker run cmd.cat/lsscsi lsscsi

Manual Page

Detailed command documentation is available at:

https://sg.danny.cz/scsi/lsscsi.html

Syntax

lsscsi [options] [H:C:T:L]

Options

-g: Show generic SCSI device file name

-k: Show kernel name instead of device node name

-d: Show major and minor numbers of the device node

-H: List SCSI hosts rather than devices

-l: Show additional information for each SCSI device

-c: Output similar to cat /proc/scsi/scsi -p: Show data integrity (protection) information

-t: Show transport information (ATA, FC, SBP, iSCSI, SPI, SAS, SATA, USB)

-L: Display additional attributes as "name=value" pairs

-v: Output directory name when information is found

-y<path>: Assume sysfs is mounted at the specified path

-s: Show human‑readable capacity size

-x: Display LUN number in hexadecimal

-P: Show valid protection mode information

-i: Show udev‑related properties

-w: Show WWN (World Wide Name)

Result Meaning

Examples

List all SCSI devices:

peng@ubuntu:~$ lsscsi
[3:0:0:0]    cd/dvd  NECVMWar VMware SATA CD01 1.00  /dev/sr0
[32:0:0:0]   disk    VMware,  VMware Virtual S 1.0   /dev/sda

Show detailed attributes:

peng@ubuntu:~$ lsscsi -L
[3:0:0:0]    cd/dvd  NECVMWar VMware SATA CD01 1.00  /dev/sr0
  device_blocked=0
  iocounterbits=32
  ...
[32:0:0:0]   disk    VMware,  VMware Virtual S 1.0   /dev/sda
  device_blocked=0
  iocounterbits=32
  ...

Show human‑readable capacity:

peng@ubuntu:~$ lsscsi -s
[3:0:0:0]    cd/dvd  NECVMWar VMware SATA CD01 1.00  /dev/sr0        -
[32:0:0:0]   disk    VMware,  VMware Virtual S 1.0   /dev/sda    536GB

Linux SCSI File Nodes

Key directories and example commands:

# /proc/scsi/
cd /proc/scsi/
ls
# Output shows device_info, mptspi, scsi, sg
cat scsi
# Sample output:
Attached devices:
Host: scsi32 Channel: 00 Id: 00 Lun: 00
  Vendor: VMware, Model: VMware Virtual S Rev: 1.0
  Type: Direct-Access  ANSI SCSI revision: 02
Host: scsi3 Channel: 00 Id: 00 Lun: 00
  Vendor: NECVMWar Model: VMware SATA CD01 Rev: 1.00
  Type: CD-ROM  ANSI SCSI revision: 05

Other useful paths:

/sys/class/scsi_host – list of SCSI host adapters

/sys/class/scsi_device – device identifiers (e.g., 3:0:0:0)

/sys/class/scsi_disk – disk devices

/sys/class/scsi_generic – generic SCSI devices (sg0, sg1)

/sys/bus/scsi – drivers and devices hierarchy

Enabling SCSI Logging

Compile the kernel with CONFIG_SCSI_LOGGING enabled.

Set the desired logging level via /proc/sys/dev/scsi/logging_level. The level is a 32‑bit bitmask where each 3‑bit field represents a logging category.

Typical values: -1 to enable all SCSI events to syslog, 0 to disable.

Example command to disable logging: echo 0 > /proc/sys/dev/scsi/logging_level Example command to enable all logging:

echo -1 > /proc/sys/dev/scsi/logging_level