Constraints

User account

You can purchase ECSs only after your account completes real-name authentication.

For details, see Real-Name Authentication.

Regions and AZs

• Resource prices vary by region. For details, see Price Calculator.
• Once ECSs are purchased, the region and AZ cannot be changed.

ECS specifications

There are quota limits for the number of ECSs, the number of vCPUs, and the memory (RAM) capacity, in MiB.

You can view the total quotas and the used quotas by referring to Service Quota. If the quotas do not meet your requirements, apply for a higher quota.

Image

Windows images are categorized as KooGallery images.

• On the Public image tab, you can select Windows to purchase third-party images provided by third parties.
• On the KooGallery image tab, you can search for and purchase Windows images.

Windows images comply with constraints from third parties, and they are billed based on the pricing details provided by third-party image providers.

For more constraints on using images, see Notes and Constraints.

Disk

• The default device type is VBD, but you can also set it to SCSI. The disk device type cannot be changed after the disk has been purchased.
• When purchasing an ECS, you can add up to 24 disks (one system disk and 23 data disks) to the ECS. After the ECS is purchased, a maximum of 60 disks can be added.

  You can attach data disks to existing ECSs if you need more data disks. To query the number of disks that can be attached to ECSs of different specifications, query information about disks attached to an ECS.

• After a data disk is attached to the ECS, you need to initialize the disk before using it.

For more constraints on using disks, see Notes and Constraints.

Network

The number of extended network interfaces that can be attached to an ECS is determined by the ECS specifications. For details, see A Summary List of x86 ECS Specifications and A Summary List of Kunpeng ECS Specifications.

For more constraints on using networks, see Notes and Constraints.

Security group

• Instances in a security group deny all external access requests by default, but you can add rules to allow specific requests.
• When adding a security group rule, grant the minimum permissions possible. For example, if remote login to an ECS over port 22 is allowed, only allow specific IP addresses to log in to the ECS. Do not use 0.0.0.0/0 (all IP addresses).

Internet

• If an ECS needs to access the Internet, bind an EIP to the ECS.
• EIPs are regional resources. Each EIP can be used by only one ECS at a time, and they must be in the same region.

For more constraints on using EIPs, see Notes and Constraints.

ECS name

• The name of a Windows ECS can contain a maximum of 15 characters and must be unique. Otherwise, some Windows applications cannot be used.
• When you set the ECS name to the OS hostname, you are advised to use letters (a-z), digits (0-9), and hyphens (-) to prevent unknown issues.

Login mode

When you select Key pair as the login mode and use an existing key pair, make sure that you have obtained the key file locally, or the login will fail.

Tag

A maximum of 10 tags can be added to an ECS.

Windows ECS

• Do not stop system processes if you are not sure about the consequences. Otherwise, blue screen of death (BSOD) or a restart may occur on the ECS.
• Ensure that there is at least 2 GiB of idle memory. Otherwise, BSOD, freezing, or service failures may occur.
• Do not modify the registry. Otherwise, the system startup may fail. If the modification is mandatory, back up the registry before modifying it.
• Do not modify ECS clock settings. Otherwise, DHCP lease may fail, leading to the loss of IP addresses.
• Do not disable virtual memory. Otherwise, system performance may deteriorate, or system exceptions may occur.
• Do not delete the VMTool program, or an exception may occur on the ECS.

Linux ECS

• Do not modify the /etc/issue file. Otherwise, the OS distribution will not be identified.
• Do not delete system directories or files. Otherwise, the system may fail to run or start.
• Do not change the permissions for or names of system directories. Otherwise, the system may fail to run or start.
• Do not upgrade the kernel of the Linux unless necessary.

  When you have to upgrade the Linux kernel, follow the instructions provided in How Can I Upgrade the Kernel of a Linux ECS?

Image boot mode

The system disk can boot from Basic Input Output System (BIOS) or Unified Extensible Firmware Interface (UEFI) according to the boot mode in the image file.

• You can create a UEFI or BIOS private image and use it to create an ECS.
• You can change the OS to convert the boot mode of the ECS.

External hardware device

Do not install external hardware devices, such as encryption dongles, USB flash drives, external hard disks, or bank USB security keys on ECSs.

Network

• Do not change the MAC address of NICs.
• Do not modify default intranet configurations, such as the IP address, subnet mask, or gateway address of an ECS. Otherwise, network exceptions may occur.
• Do not change the default DNS server address. If you need to configure a public DNS address, configure both a public and a private DNS address on your ECS.
• Manually specified IP addresses for Linux ECSs are generally static IP addresses. To avoid network exceptions caused by conflicts between NetworkManager and internal network services, do not enable NetworkManager when not required, such as when installing Kubernetes.

Application program software

• Do not uninstall drivers on the ECS hardware.
• Do not install virtualization software on ECSs for nested virtualization.
• Do not delete the CloudResetPwdAgent or CloudResetPwdUpdateAgent process. Otherwise, one-click password reset will become unavailable.

Migration

• Do not deploy applications on a single ECS if you require high availability. Set up auto start for your ECSs or deploy applications in cluster or active/standby mode.
• Do not associate software licenses with the physical server hosting an ECS. Once an ECS is migrated from one physical server to another, the associated licenses may become invalid.

Data backup

Data on ECSs running core applications needs to be backed up.