github.com/cosmos/cosmos-sdk@v0.50.10/docs/docs/build/building-modules/08-genesis.md (about)

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     2  sidebar_position: 1
     3  ---
     4  
     5  # Module Genesis
     6  
     7  :::note Synopsis
     8  Modules generally handle a subset of the state and, as such, they need to define the related subset of the genesis file as well as methods to initialize, verify and export it.
     9  :::
    10  
    11  :::note Pre-requisite Readings
    12  
    13  * [Module Manager](./01-module-manager.md)
    14  * [Keepers](./06-keeper.md)
    15  
    16  :::
    17  
    18  ## Type Definition
    19  
    20  The subset of the genesis state defined from a given module is generally defined in a `genesis.proto` file ([more info](../../learn/advanced/05-encoding.md#gogoproto) on how to define protobuf messages). The struct defining the module's subset of the genesis state is usually called `GenesisState` and contains all the module-related values that need to be initialized during the genesis process.
    21  
    22  See an example of `GenesisState` protobuf message definition from the `auth` module:
    23  
    24  ```protobuf reference
    25  https://github.com/cosmos/cosmos-sdk/blob/v0.50.0-alpha.0/proto/cosmos/auth/v1beta1/genesis.proto
    26  ```
    27  
    28  Next we present the main genesis-related methods that need to be implemented by module developers in order for their module to be used in Cosmos SDK applications.
    29  
    30  ### `DefaultGenesis`
    31  
    32  The `DefaultGenesis()` method is a simple method that calls the constructor function for `GenesisState` with the default value for each parameter. See an example from the `auth` module:
    33  
    34  ```go reference
    35  https://github.com/cosmos/cosmos-sdk/blob/v0.50.0-alpha.0/x/auth/module.go#L63-L67
    36  ```
    37  
    38  ### `ValidateGenesis`
    39  
    40  The `ValidateGenesis(data GenesisState)` method is called to verify that the provided `genesisState` is correct. It should perform validity checks on each of the parameters listed in `GenesisState`. See an example from the `auth` module:
    41  
    42  ```go reference
    43  https://github.com/cosmos/cosmos-sdk/blob/v0.50.0-alpha.0/x/auth/types/genesis.go#L62-L75
    44  ```
    45  
    46  ## Other Genesis Methods
    47  
    48  Other than the methods related directly to `GenesisState`, module developers are expected to implement two other methods as part of the [`AppModuleGenesis` interface](./01-module-manager.md#appmodulegenesis) (only if the module needs to initialize a subset of state in genesis). These methods are [`InitGenesis`](#initgenesis) and [`ExportGenesis`](#exportgenesis).
    49  
    50  ### `InitGenesis`
    51  
    52  The `InitGenesis` method is executed during [`InitChain`](../../learn/advanced/00-baseapp.md#initchain) when the application is first started. Given a `GenesisState`, it initializes the subset of the state managed by the module by using the module's [`keeper`](./06-keeper.md) setter function on each parameter within the `GenesisState`.
    53  
    54  The [module manager](./01-module-manager.md#manager) of the application is responsible for calling the `InitGenesis` method of each of the application's modules in order. This order is set by the application developer via the manager's `SetOrderGenesisMethod`, which is called in the [application's constructor function](../../learn/beginner/00-app-anatomy.md#constructor-function).
    55  
    56  See an example of `InitGenesis` from the `auth` module:
    57  
    58  ```go reference
    59  https://github.com/cosmos/cosmos-sdk/blob/v0.50.0-alpha.0/x/auth/keeper/genesis.go#L8-L35
    60  ```
    61  
    62  ### `ExportGenesis`
    63  
    64  The `ExportGenesis` method is executed whenever an export of the state is made. It takes the latest known version of the subset of the state managed by the module and creates a new `GenesisState` out of it. This is mainly used when the chain needs to be upgraded via a hard fork.
    65  
    66  See an example of `ExportGenesis` from the `auth` module.
    67  
    68  ```go reference
    69  https://github.com/cosmos/cosmos-sdk/blob/v0.50.0-alpha.0/x/auth/keeper/genesis.go#L37-L49
    70  ```
    71  
    72  ### GenesisTxHandler
    73  
    74  `GenesisTxHandler` is a way for modules to submit state transitions prior to the first block. This is used by `x/genutil` to submit the genesis transactions for the validators to be added to staking. 
    75  
    76  ```go reference
    77  https://github.com/cosmos/cosmos-sdk/blob/v0.50.0-alpha.0/core/genesis/txhandler.go#L3-L6
    78  ```