Help Center/ Elastic Cloud Server/ API Reference/ APIs (Recommended)/ Status Management/ Reinstalling an ECS OS (Using an Image Without Cloud-Init Installed)
Updated on 2026-03-18 GMT+08:00
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Reinstalling an ECS OS (Using an Image Without Cloud-Init Installed)

Function

This API is used to reinstall an ECS OS.

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.

This API supports the images without Cloud-Init or Cloudbase-Init installed. Otherwise, use the API described in Reinstalling an ECS OS (Using an Image with Cloud-Init Installed).

Constraints

  • ECSs without system disks do not support OS reinstallation.
  • You are not allowed to perform other operations when reinstalling the OS, or the OS reinstallation may fail.

URI

POST /v1/{project_id}/cloudservers/{server_id}/reinstallos

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

Parameter

Mandatory

Description

project_id

Yes

Definition

Specifies the project ID.

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

Constraints

N/A

Range

N/A

Default Value

N/A

server_id

Yes

Definition

Specifies the ECS ID.

Constraints

N/A

Range

N/A

Default Value

N/A

Request

Table 2 describes the request parameters.
Table 2 Request parameters

Parameter

Mandatory

Type

Description

os-reinstall

Yes

Object

Definition

Reinstall the ECS. 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 Linux administrator username is root.

Constraints

  • Either adminpass or keyname is empty.
  • Either adminpass or keyname is set.

Range

Password complexity requirements:

  • 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 Listing SSH Key Pairs).

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 the metadata of the ECS for which the OS is to be reinstalled.

For more information, see Table 4.

Constraints

N/A

Range

N/A

Default Value

N/A

mode

No

String

Definition

When this parameter is set to withStopServer, you can submit the OS reinstallation request when the ECS is running.

Constraints

N/A

Range

When mode is set to withStopServer, the system will stop the running ECS first before reinstalling the OS.

Default Value

N/A
Table 4 metadata field description

Parameter

Mandatory

Type

Description

__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 Key List.

Range

N/A

Default Value

N/A

Response

Table 5 describes the response parameters.

Table 5 Response parameters

Parameter

Type

Description

job_id

String

Definition

Specifies the job ID returned after a job is delivered. The job ID can be used to query the job execution progress. For details about how to query the job execution status based on job_id, see Job Status Management.

Range

N/A

For details about abnormal responses, see Responses (Jobs).

Example Request

Reinstall an OS and use the key pair for login authentication after the reinstallation.

POST https://{endpoint}/v1/{project_id}/cloudservers/{server_id}/reinstallos

{
    "os-reinstall": {
        "keyname": "KeyPair-350b", 
        "userid": "7e25b1da389f4697a79df3a0e5bd494e"
    }
}

Example Response

See Responses (Jobs).

{      
    "job_id": "ff80808288d41e1b018990260955686a" 
}

Returned Values

See Returned Values for General Requests.

Error Codes

See Error Codes.

Parent topic: Status Management