Is uuid necessary in centos?

Uuid in centos is necessary; uuid is the abbreviation of "Universally Unique Identifier". It is a standard for software construction and a globally unique identifier at the system level. Its function is to allow distribution All elements in the system can have unique identification information, without the need to specify identification information through a central control terminal.

The operating environment of this article: centos 7 system, Dell G3 computer.

Uuid in centos is necessary

In centos7, uuid is a universal unique identification code and a standard for software construction. The function of uuid is to allow all elements in the distributed system to All can have unique identification information, without the need to specify the identification information through the central control terminal.

UUID is the abbreviation of Universally Unique Identifier. It is a standard for software construction and a globally unique identifier at the system level. It is also a distributed system organized by the Open Software Foundation. Part of the field of computing environments.

The purpose is to enable all elements in the distributed system to have unique identification information, without the need for the central control terminal to specify identification information. This way, everyone can create UUIDs that don't conflict with anyone else's. In this case, there is no need to consider the duplication of names when creating the database. The most widely used UUID is Microsoft's Globally Unique Identifier (GUID), while other important applications include Linux ext2/ext3 file system, LUKS encrypted partition, GNOME, KDE, Mac OS X, etc. In addition, we can also find the implementation in the UUID library in the e2fsprogs package.

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Definition

UUID is the International Organization for Standardization (ISO) A concept proposed. UUID is a 128-bit value, which can be calculated through a certain algorithm. To improve efficiency, commonly used UUIDs can be shortened to 16 bits. UUID is used to identify attribute types and is regarded as a unique identifier across all space and time. Generally speaking, it is guaranteed that this value is truly unique and any UUID generated anywhere will not have the same value. One benefit of using UUIDs is that new identifiers can be created for new services. In this way, when the client is looking for a service, it only needs to point out the UUID related to a certain type of service (or a specific service) in its service lookup request. If the service provider can match the available services with this UUID If there is a match, a response is returned.

UUID is calculated and generated based on data such as the current time, counter and hardware identification (usually the MAC address of the wireless network card). UUIDs can be independently created by anyone and published on demand. There is no centralized authority for UUIDs because they are unique identifiers that cannot be copied. The property protocol allows devices to use UUIDs to identify property types, eliminating the need for read/write requests to identify their local handles.

Composition

UUID refers to a number generated on one machine, which is guaranteed to be unique to all machines in the same time and space. Usually the platform will provide a generated API. Calculated in accordance with the standards set by the Open Software Foundation (OSF), the Ethernet card address, nanosecond time, chip ID code and random number are used.

UUID is a combination of the following parts:

(1) The first part of UUID is related to time. If you generate a UUID after a few seconds, then The first part is different, the rest are the same.

(2) Clock sequence.

(3) Globally unique IEEE machine identification number. If there is a network card, it is obtained from the MAC address of the network card. If there is no network card, it is obtained by other means.

The only drawback of UUID is that the generated result string will be relatively long. The most commonly used UUID standard is Microsoft's GUID (Globals Unique Identifiers). In ColdFusion, you can use the CreateUUID() function to easily generate a UUID. Its format is: xxxxxxxx-xxxx- xxxx-xxxxxxxxxxxxxxxx (8-4-4-16), where each x is one in the range of 0-9 or a-f. Hexadecimal number. The standard UUID format is: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx (8-4-4-4-12). You can download the CreateGUID() UDF from cflib for conversion.

(4) In hibernate (Java orm framework), it is composed of IP-JVM startup time-current time shifted right by 32 bits-current time-internal count (8-8-4-8-4) UUID

Recommended tutorial: "centos tutorial"

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