# appspawn Module for the Standard System ## Overview After being started by the init process, the appspawn process waits for inter-process communication (IPC) messages. Upon receiving a message, the appspawn process starts an application service based on the message content, and grants the corresponding permission to the application service. ### Introduction - Security control
Support for setting of SELinux tags for applications - Application process control - Support for setting of AccessToken for applications - Support for simultaneous stopping of all spawn application processes (after stopping of the appspawn process and before a restart) - Cold start
Support for cold start of applications by using the **aa** command ``` param set appspawn.cold.boot true // Enable cold start. aa start -d 12345 -a $name -b $package -C Example: aa start -d 12345 -a ohos.acts.startup.sysparam.function.MainAbility -b ohos.acts.startup.sysparam.function -C ### Basic Concepts **appspawn** is a registered service name. The appspawn process receives requests from the client by listening to messages over the local socket. The message type is an **AppProperty** structure. It is defined in **base/startup/appspawn_standard/interfaces/innerkits/include/sclient_socket.h**. **Table 1** Field description

Field

Description

processName

Name of the service process to be started. The value contains a maximum of 256 bytes.

bundleName

Bundle name of the application to be started. The value contains a maximum of 256 bytes.

soPath

Path of the dynamic library specified by the application. The value contains a maximum of 256 bytes.

uid

UID of the application process to be started. The value must be a positive number.

gid

GID of the application process to be started. The value must be a positive number.

gidTable

Information about the application process group to be started. Its length is specified by gidCount. A maximum of 64 process groups are supported. The value must be a positive number.

gidCount

Number of application process groups to be started.

accessTokenId

Token ID for application process permission control.

apl

APL for application process permission control. The value contains a maximum of 32 bytes.
## Development Guidelines The API definitions are provided in **base/startup/appspawn_standard/interfaces/innerkits/include/client_socket.h**. Table 2 is a list of available APIs. ### Available APIs **Table 2** API description

API

Description

CreateClient

Creates a client.

CloseClient

Closes a client.

ConnectSocket

Sends a connection request to the appspawn service.

WriteSocketMessage

Sends a message to the appspawn service.

ReadSocketMessage

Receives a message from the appspawn service.
### Development Example
The following is an example of using related APIs: ``` std::shared_ptr clientSocket = std::make_unique("AppSpawn"); if (clientSocket == nullptr) { return -1; } if (clientSocket->CreateClient() != ERR_OK) { return -1; } if (clientSocket->ConnectSocket() != ERR_OK) { return -1;; } // Construct AppProperty based on the specified property. clientSocket->WriteSocketMessage((void *)&property, sizeof(AppSpawn::AppProperty)); // Read the result. int pid; clientSocket->ReadSocketMessage((void *)&pid, sizeof(pid)); // Normally, the process ID of the application is returned. If the PID is less than or equal to 0, an error has occurred. ``` ## FAQ ### Cold Start Failure   **Symptom**
    Cold start failed because of a command execution failure.   **Solution**
    1. Check whether cold start is enabled.
    2. Check whether the cold start command is correct.