What kind of device does linux usb belong to?-Linux Operation and Maintenance-php.cn

Linux usb is a block device. Block devices are devices that must be accessed in blocks when performing TO operations in Linux systems. Block devices can install file systems; common block devices in Linux systems include hard disks, floppy drives, Blu-ray discs, USB disks, etc. Block devices are mainly designed for slow devices such as disks to avoid consuming too much CPU time waiting.

What kind of device does linux usb belong to?

#The operating environment of this tutorial: linux7.3 system, Dell G3 computer.

What kind of device does linux usb belong to?

Linux usb is a block device.

Linux divides devices into three categories according to information organization characteristics, which are:

Character devices:

Send in character units Or receive a character stream regardless of any block structure. Character devices are not addressable and do not have seek operations. For example, printer, network interface, mouse.
Block device:

Block device is a device that must be accessed in blocks when performing TO operations in the Linux system. Block devices can install file systems. The block device driver will use a piece of system memory as a buffer, so issuing read and write accesses to the block device does not necessarily result in hardware I/O operations immediately. Common block devices in Linux systems include hard disks, floppy drives, Blu-ray discs, USB disks, etc.
Network equipment:

The network device can be either a hardware device such as a network card or a pure software device such as a loopback device. Network devices are driven by the Linux network subsystem and are responsible for sending and receiving data packets, rather than stream devices. Therefore, network devices do not have nodes in the Linux system file system. Access to network devices is generated through socket calls, rather than ordinary file operations such as open/closc and read/write.

The difference between block devices and character devices:

Character devices can only be read sequentially, while block devices can be read randomly;

Block devices are read through the system cache, not directly from the physical disk. Character devices can read physical disks directly without going through the system cache. When a read/write request is issued to a character device, the actual hardware I/O usually occurs immediately, while the block device uses a piece of system memory as a buffer. When the user process's request for the device can meet the user's requirements, the request is returned. If the data cannot be obtained, call the request function to perform the actual I/O operation. Therefore, block devices are mainly designed for slow devices such as disks to avoid consuming too much CPU time waiting;

In the operating system device management function, devices are classified as exclusive devices, shared devices, and virtual devices For device allocation, exclusive devices include all character devices, and shared devices include all block devices.

Linux View block device information

In Linux, you can use the lsblk command to view block device information.

The lsblk command in English is "list block", which is used to list information about all available block devices, and also displays the dependencies between them, but it does not list RAM disk information. Block devices include hard disks, flash drives, CD-ROMs, etc. The lsblk command is included in the util-linux-ng package, which is now renamed util-linux.

The lsblk command has several options:

Default Options

The lsblk command will list all block devices in a tree view by default. Open the terminal and enter the following command:

$ lsblk

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The output is as follows:

lsblk default
lsblk default

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The 7 column names are as follows:

NAME : 这是块设备名。
MAJ:MIN : 本栏显示主要和次要设备号。
RM : 本栏显示设备是否可移动设备。注意，在本例中设备sdb和sr0的RM值等于1，这说明他们是可移动设备。
SIZE : 本栏列出设备的容量大小信息。例如298.1G表明该设备大小为298.1GB，而1K表明该设备大小为1KB。
RO : 该项表明设备是否为只读。在本案例中，所有设备的RO值为0，表明他们不是只读的。
TYPE :本栏显示块设备是否是磁盘或磁盘上的一个分区。在本例中，sda和sdb是磁盘，而sr0是只读存储（rom）。（LCTT译注，此处sr0的RO项没有标记为1，可能存在一些错误？）
MOUNTPOINT : 本栏指出设备挂载的挂载点。

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List all devices:

The default option will not list all empty devices. To view these empty devices, use the following command:

$ lsblk -a

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This option will list all devices, including empty devices.

lsblk bytes sda
lsblk bytes sda

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List device permissions and owners:

The lsblk command can also be used to list the ownership of a specific device, as well as groups and modes. . You can obtain this information through the following command:

$ lsblk -m
lsblk permissions
lsblk permissions

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List the specified device:

This command can also obtain only the information of the specified device. This is accomplished by specifying the device name after the options provided to the lsblk command. For example, you might be interested in knowing the size of your disk drive in bytes. You can do this by running the following command:

$ lsblk -b /dev/sda

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Alternatively, the following command is equivalent:

$ lsblk --bytes /dev/sda

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List unheaded devices in list form:

You can also combine several options to get specific output. For example, you might want to list devices in a list format instead of the default tree format. You may also be interested in removing headers for different column names. Two different options can be combined to get the desired output with the command:

$ lsblk -nl

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Alternatively, you can use the long options below which also give the same output.

$ lsblk --noheadings --list
lsblk no header and list
lsblk no header and list

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List SCSI devices:

To get a list of SCSI devices, you can only use the -S option. This option is a capital S and should not be confused with the -s option, which prints dependencies in reverse order.