Detailed explanation of Linux command lsscsi

To understand the lsscsi command, first we need to understand what SCSI is and common hard disk interfaces and common hard disk parameters.

1. What is SCSI?

SCSI (Small Computer System Interface) is a complete data transfer protocol, which is mainly used to transfer commands, status and block data between the host and storage devices. Among various storage technologies, SCSI technology is the most important pillar.

The SCSI protocol is located between the operating system and external resources. It has a series of functional components. The operating system's I/O operations on external devices (such as disks, tapes, CD-ROMs, printers , etc.) can be implemented through the SCSI protocol. Typically, the SCSI protocol is embedded in the device driver or the host adapter's onboard logic.

2. Common hard disk interfaces

1. Hard drive with IDE interface

Its English name: Integrated Drive Electronics, the common 2.5-inch IDE hard disk interface, its original meaning refers to the hard disk drive that integrates the "hard disk controller" and the "disk body".

IDE represents a type of hard disk, but in actual applications, people are also accustomed to using IDE to refer to the earliest IDE type hard disk ATA-1. This type of interface has been eliminated with the development of interface technology. , and then developed into more types of hard disk interfaces, such as ATA, Ultra ATA, DMA, Ultra DMA and other interfaces, which are all IDE hard disks.

Its characteristics are: low price, strong compatibility, high cost performance, slow data transmission, does not support hot swapping, etc.

2. SCSI interface hard disk

SCSI is not an interface specifically designed for hard disks. It is a high-speed data transmission technology widely used on minicomputers.

The SCSI interface has the advantages of wide application range, multi-tasking, large bandwidth, low CPU usage, and hot-swappability. However, the higher price makes it difficult to be as popular as IDE hard drives, so SCSI hard drives are mainly used in medium and , high-end servers and high-end workstations.

Its characteristics are: high transmission rate, good reading and writing performance, can connect multiple devices, and can support hot swapping, but the price is relatively expensive.

3. SATA interface type

The English name is: Serial Advanced Technology Attachment. Hard drives using the SATA (Serial ATA) port are also called serial hard drives and are the future trend of PC hard drives.

Serial ATA uses a serial connection method. The Serial ATA bus uses an embedded clock signal and has stronger error correction capabilities. Compared with the past, its biggest difference is that it can transmit instructions (not just data). Check and automatically correct errors if found, which greatly improves the reliability of data transmission.

The serial interface also has the advantages of simple structure and support for hot swapping.

3. lsscsi command

lsscsi lists scsi/sata device information, such as hard drives and optical drives.

1. lsscsi command installation

-bash: lsscsi command not found
 
#Debian
apt-get install lsscsi
 
#Ubuntu
apt-get install lsscsi
 
#Alpine
apk add lsscsi
 
#Arch Linux
pacman -S lsscsi
 
#Kali Linux
apt-get install lsscsi
 
#CentOS
yum install lsscsi
 
#Fedora
dnf install lsscsi
 
#Raspbian
apt-get install lsscsi
 
#Docker
docker run cmd.cat/lsscsi lsscsi

2. lsscsi command English manual

Detailed command description address

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

2. Command format

lsscsi command syntax:

lsscsi [选项] [H:C:T:L]

lsscsi command options:

Options	meaning
-g	Display SCSI common device file name
-k	Display kernel name instead of device node name
-d	Display the primary and secondary numbers of the device node
-H	List the SCSI hosts currently connected to the system instead of the SCSI devices
-l	Display additional information for each SCSI device (host)
-c	Relative to the output of executing cat /proc/scsi/scsi command
-p	Show additional data integrity (protection) information
-t	Display transmission information
-L	Display additional information in the form of "attribute name=value"
-v	Output directory name when information is found
-y	Assume that sysfs is mounted at the specified path instead of the default "/sys"
-s	Display capacity size.
-c	Display the default information with the full name.
-d	Display the device primary and secondary device numbers.
-g	Display the corresponding sg device name.
-H	Display host controller list, -Hl, -Hlv.
-l	Display related attributes, -ll,-llll=-L.
-v	Display the directory where the device properties are located.
-x	Display the lun number in hexadecimal.
-p	Output DIF,DIX protection type.
-P	Output valid protection mode information.
-i	Display udev related attributes
-w	Show WWN
-t	Display corresponding transmission information (ATA, FC, SBP, ISCSI, SPI, SAS, SATA, USB), -Ht, -tl. (including sas address)

3. 结果含义

四、命令举例

lsscsi 列出所有 SCSI 设备：

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 

lsscsi -L列出所有具有详细属性的 SCSI 设备：

peng@ubuntu:~$ lsscsi -L
[3:0:0:0]    cd/dvd  NECVMWar VMware SATA CD01 1.00  /dev/sr0 
  device_blocked=0
  iocounterbits=32
  iodone_cnt=0x229
  ioerr_cnt=0x4
  iorequest_cnt=0x23a
  queue_depth=1
  queue_type=none
  scsi_level=6
  state=running
  timeout=30
  type=5
[32:0:0:0]   disk    VMware,  VMware Virtual S 1.0   /dev/sda 
  device_blocked=0
  iocounterbits=32
  iodone_cnt=0x37370
  ioerr_cnt=0x3
  iorequest_cnt=0x37370
  queue_depth=32
  queue_type=simple
  scsi_level=3
  state=running
  timeout=180
  type=0

lsscsi -s列出所有具有人类可读磁盘容量的 SCSI 设备：

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

五、其他

1. Linux下scsi相关文件节点

/proc/scsi/

peng@ubuntu:~$ cd /proc/scsi/
peng@ubuntu:/proc/scsi$ ls
device_info  mptspi  scsi  sg

peng@ubuntu:/proc/scsi$ cat scsi
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

/sys/class/scsi_host

peng@ubuntu:/sys/class/scsi_host$ ls
host0   host12  host16  host2   host23  host27  host30  host5  host9
host1   host13  host17  host20  host24  host28  host31  host6
host10  host14  host18  host21  host25  host29  host32  host7
host11  host15  host19  host22  host26  host3   host4   host8

/sys/class/scsi_device

peng@ubuntu:/sys/class/scsi_device$ ls
3:0:0:0  32:0:0:0

/sys/class/scsi_disk

peng@ubuntu:/sys/class/scsi_disk$ ls
32:0:0:0

/sys/class/scsi_generic

peng@ubuntu:/sys/class/scsi_generic$ ls
sg0  sg1

/sys/bus/scsi

peng@ubuntu:/sys/bus/scsi$ ls
devices  drivers  drivers_autoprobe  drivers_probe  uevent
peng@ubuntu:/sys/bus/scsi/devices$ ls
3:0:0:0   host11  host16  host20  host25  host3   host5  target3:0:0
32:0:0:0  host12  host17  host21  host26  host30  host6  target32:0:0
host0     host13  host18  host22  host27  host31  host7
host1     host14  host19  host23  host28  host32  host8
host10    host15  host2   host24  host29  host4   host9

其中target3:0:0

对应

host:bus:id:lun

2. Linux 开启 SCSI 日志调试功能

• 1.编译选项中需开启 CONFIG_SCSI_LOGGING

• 2.该编译选项说明

drivers/scsi/Kconfig:213
config SCSI_LOGGING
    bool "SCSI logging facility"
    depends on SCSI
    ---help---
      This turns on a logging facility that can be used to debug a number
      of SCSI related problems.

      If you say Y here, no logging output will appear by default, but you
      can enable logging by saying Y to "/proc file system support" and
      "Sysctl support" below and executing the command

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

      where  is a four byte value representing the logging type
      and logging level for each type of logging selected.

      There are a number of logging types and you can find them in the
      source at . The logging levels
      are also described in that file and they determine the verbosity of
      the logging for each logging type.

      If you say N here, it may be harder to track down some types of SCSI
      problems. If you say Y here your kernel will be somewhat larger, but
      there should be no noticeable performance impact as long as you have
      logging turned off.

• 3.logging 类型源码文件位置（有说明）

-> drivers\scsi\scsi_logging.h

• 4.使用说明

/*
 * Note - the initial logging level can be set here to log events at boot time.
 * After the system is up, you may enable logging via the /proc interface.
 */
unsigned int scsi_logging_level;
#if defined(CONFIG_SCSI_LOGGING)
EXPORT_SYMBOL(scsi_logging_level);
#endif

scsi_logging_level 被定义成int类型（32bit），该机制使用了30个bit，从低位到高位每3bit为一个logging level从SCSI_LOG_ERROR_SHIFT到SCSI_LOG_IOCTL_SHIFT（SCSI_LOG_XXX_SHIFT为不同level的移位数），每个level使用的bit数都是3，所以 SCSI_LOG_XXX_BITS 均为3

• 5.scsi_logging_level 值可以在 boot 命令行设置也可以开启设备后在 /proc 文件系统中设置：

-1   - Enable scsi events to syslog.         // 开启所有scsi log
0    - Disable scsi events to syslog.        // 关闭所有scsi log

命令:

echo 0/-1 > /proc/sys/dev/scsi/logging_level

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