# Session leader

A session leader is a linux process, which is forked from [init](init.md) after receiving a `LxInitMessageCreateSession` message (see `src/linux/init.cpp`)

## Creating linux processes

Session leaders are used to create linux processes on behalf of the user. Each linux session leader is associated to a Windows console. 

To create a user process, [wslservice.exe](wslservice.exe.md) sends a `LxInitMessageCreateProcess` message (WSL1) or a `LxInitMessageCreateProcessUtilityVm` message (WSL2), which contains details about the process to create such as:

- Command line
- Current directory
- Environment variables 
- User name

### Creating a WSL1 process

When running in a WSL1 distribution, the session leader forks(), and uses the child process to `exec()` into the user linux process. Before calling `exec()`, child configures various settings such as:

- The user and group id
- The current directory
- The standard file descriptors (stdin, stdout, stderr)

### Creating a WSL2 process

When running in a WSL2 distribution, the session leader forks() to create a [relay](relay.md) process, which is responsible for creating the user process and relaying its output back to [wsl.exe](wsl.exe.md)