A boot mode refers to the method of booting the system disk when a CVM instance is created. You can find this information in the image parameters.
CVM supports two types of boot modes: Legacy Basic Input/Output System (BIOS) and Unified Extensible Firmware Interface (UEFI). This document describes the differences between these boot modes and details the boot modes supported by CVM instances.
Differences Between Legacy BIOS and UEFI
| Comparison Item | UEFI | Legacy BIOS |
|---|---|---|
| System Boot Process | UEFI uses GUID Partition Table (GPT) as the partitioning scheme, supporting hard disks larger than 2 TB and multiple partitions. | Legacy BIOS uses Master Boot Record (MBR) as the partitioning scheme, supporting hard disks up to 2 TB and a maximum of four primary partitions. |
| Boot Speed | UEFI offers faster boot speed as it can directly interact with the operating system. | Legacy BIOS requires a boot loader to load the operating system. |
| Secure Boot | UEFI provides the Secure Boot feature to prevent unauthorized operating systems and boot loaders from start. | Legacy BIOS does not have a Secure Boot feature similar to that of UEFI. |
| Interfaces and Operations | UEFI provides a graphical interface and richer operational options. | Legacy BIOS typically provides a basic text-mode interface. |
| Compatibility | UEFI is a newer technology that supports more hardware devices and operating systems. | Legacy BIOS is an older technology that may encounter compatibility issues with certain new hardware devices and operating systems. |
| Firmware Size | UEFI firmware is typically greater than Legacy BIOS firmware because it includes more features and drivers. | Legacy BIOS firmware is smaller than UEFI firmware. |
| System Diagnosis and Recovery | UEFI boot mode typically provides more system diagnosis and recovery tools, helping repair and recover the system more easily when issues occur. | Legacy BIOS has fewer system diagnosis and recovery tools than UEFI. |
Description of Boot Mode for Public Images
Public images with the "UEFI Edition" suffix in their names use the UEFI boot mode (such as TencentOS Server 3.1 (TK4) UEFI Edition). Those without the "UEFI Edition" suffix use the Legacy BIOS boot mode.
You can also go to the CVM console > Images page, click the image ID, and view the details on the details page.
Description of Boot Mode for Custom Images
- Importing a custom image: You can configure the boot mode of the image.
Ensure that the currently selected boot mode is consistent with that of the image file. Otherwise, using this image may affect the boot of your instance. - Creating a custom image: The boot mode of the image currently used by your instance will be inherited.
You can also go to the CVM console > Images page, click the image ID, and view the details on the details page.