Help Center/ Elastic Cloud Server/ API Reference/ APIs/ Status Management/ Reinstalling an ECS OS (Using an Image with Cloud-Init Installed)
Updated on 2025-08-20 GMT+08:00

Reinstalling an ECS OS (Using an Image with Cloud-Init Installed)

Function

This API is used to reinstall an ECS OS. During the system disk reinstallation using the original image, the data disks of the ECS remain unchanged.

This API is an asynchronous API. After the OS reinstallation request is successfully delivered, a job ID is returned. This does not mean the reinstallation is complete. You need to call the API by referring to Querying Job Execution Status to query the job status. The SUCCESS status indicates that the reinstallation is successful.

After this API is called, the system uninstalls the system disk, uses the original image to create a system disk, and attaches it to the ECS. In this way, the OS is reinstalled.

Constraints

  • You can only use an image with Cloud-Init or Cloudbase-Init installed. If the image has no Cloud-Init or Cloudbase-Init installed, use the API described in Reinstalling an ECS OS (Using an Image Without Cloud-Init Installed).
  • You are not allowed to reinstall the OS of an ECS that does not have the system disk.
  • You are not allowed to perform other operations when reinstalling the OS. Otherwise, reinstalling the OS will fail.

URI

POST /v2/{project_id}/cloudservers/{server_id}/reinstallos

Table 1 describes the parameters in the URI.
Table 1 Parameter description

Parameter

Mandatory

Description

project_id

Yes

Specifies the project ID.

For details about how to obtain the ID, see Obtaining a Project ID.

server_id

Yes

Specifies the ECS ID.

Request

Table 2 describes the request parameters.
Table 2 Request parameters

Parameter

Mandatory

Type

Description

os-reinstall

Yes

Object

Definition

Re-installs an ECS OS. For details, see Table 3.

Constraints

N/A

Range

N/A

Default Value

N/A

Table 3 os-reinstall field description

Parameter

Mandatory

Type

Description

adminpass

No

String

Definition

Specifies the initial password of the ECS administrator.

The Windows administrator username is Administrator, and the Linux administrator username is root.

Constraints

  • The Windows ECS password cannot contain the username, the username in reverse, or more than two characters in the same sequence as they appear in the username.
  • Linux ECSs can use user_data to inject passwords. In such a case, adminpass is unavailable.
  • Either adminpass or keyname is specified.
  • If both adminpass and keyname are empty, user_data in metadata must be set.

Range

  • The password must contain 8 to 26 characters.
  • The password must contain at least three of the following character types: uppercase letters, lowercase letters, digits, and special characters (!@$%^-_=+[{}]:,./?~#*).

Default Value

N/A

keyname

No

String

Definition

Specifies the key name.

Keys can be created using the key creation API (see Creating and Importing an SSH Key Pair) or obtained using the SSH key query API (see Querying the SSH Key Pair List).

Constraints

N/A

Range

N/A

Default Value

N/A

userid

No

String

Definition

Specifies the user ID.

Constraints

N/A

Range

N/A

Default Value

N/A

metadata

No

Object

Definition

Specifies metadata of the reinstalled ECS.

For more information, see Table 4.

Constraints

N/A

Range

N/A

Default Value

N/A

mode

No

String

Definition

Specifies whether the ECS supports OS reinstallation when the ECS is running.

Constraints

N/A

Range

If the parameter value is withStopServer, the ECS supports OS reinstallation when the ECS is running. In such a case, the system automatically stops the ECS before reinstalling its OS.

Default Value

N/A

Table 4 metadata field description

Parameter

Mandatory

Type

Description

BYOL

No

String

Definition

If you have an OS or a software license (a license certified based on the number of physical servers and cores), you can migrate your services to the cloud platform in BYOL mode to continue using your existing licenses.

Constraints

N/A

Range
  • true: Use your existing licenses.
  • Other values are invalid and an error will be reported.

Default Value

N/A

user_data

No

String

Definition

Specifies the user data to be injected to the ECS during the creation. Text and text files can be injected.

Examples

Before base64 encoding:

  • Linux
    #!/bin/bash
    echo user_test > /home/user.txt
  • Windows
    rem cmd
    echo 111 > c:\aaa.txt

After base64 encoding:

  • Linux
    IyEvYmluL2Jhc2gKZWNobyB1c2VyX3Rlc3QgPiAvaG9tZS91c2VyLnR4dA==
  • Windows
    cmVtIGNtZAplY2hvIDExMSA+IGM6XGFhYS50eHQ=

For more details, see Injecting User Data into ECSs.

Constraints

  • The content of user_data must be encoded with base64.
  • The maximum size of the content to be injected (before encoding) is 32 KB.

Range

N/A

Default Value

N/A

__system__encrypted

No

String

Definition

Specifies the encryption field in metadata.

Constraints

N/A

Range

  • 0: indicates a non-encrypted disk.
  • 1: indicates an encrypted disk.

Default Value

If this parameter does not exist, the system disk will not be encrypted by default.

__system__cmkid

No

String

Definition

Specifies the CMK ID, which indicates encryption in metadata.

Constraints

This parameter must be used with __system__encrypted.

NOTE:

For details about how to obtain the CMK ID through HTTPS requests, see Querying the List of CMKs.

Range

N/A

Default Value

N/A

Response

See Responses (Task).

Example Request

  • After the ECS OS is reinstalled, use the password for login authentication. For security purposes, store the password in ciphertext in configuration files or environment variables.
    POST https://{endpoint}/v2/{project_id}/cloudservers/{server_id}/reinstallos
    
    {
        "os-reinstall": {
            "adminpass": "$ADMIN_PASS",
            "userid": "7e25b1da389f4697a79df3a0e5bd494e",
            "mode": "withStopServer"
        }
    }
  • Reinstall an OS and use the key pair for login authentication after the reinstallation.
    POST https://{endpoint}/v2/{project_id}/cloudservers/{server_id}/reinstallos
    
    {
        "os-reinstall": {
            "keyname": "KeyPair-350b", 
            "userid": "7e25b1da389f4697a79df3a0e5bd494e"
        }
    }
  • If the ECS OS is reinstalled using encrypted full-ECS images of the system disk, use the password for login authentication. For security purposes, store the password in ciphertext in configuration files or environment variables.
    POST https://{endpoint}/v2/{project_id}/cloudservers/{server_id}/reinstallos
    
    {
        "os-reinstall": { 
            "adminpass": "$ADMIN_PASS",
            "userid": "7e25b1da389f4697a79df3a0e5bd494e",
            "metadata": {
                  "__system__encrypted": "1",
                  "__system__cmkid": "83cdb52d-9ebf-4469-9cfa-e7b5b80da846"
            }
        }
    }

Example Response

See Responses (Task).

{      
    "job_id": "ff80808288d41e1b018990260955686a" 
}

Error Codes

See Error Codes.