Once `yarn start` has built the assets it will continue to do so whenever any of the files change. This means you don't have to manually build the assets whenever you've made a change to the code.
Next, we'll build the web server that will serve the frontend assets we just built.
### Backend
Build and run the backend, by running `make run` in the root directory of the repository. This command will compile the Go source code, and start a web server.
The end-to-end tests in Grafana uses [puppeteer](https://github.com/GoogleChrome/puppeteer) to run automated scripts in a headless Chrome browser. To run the tests:
```
yarn e2e-tests
```
By default, the end-to-end tests assumes Grafana is available on `localhost:3000`. To use a specific URL, set the `BASE_URL` environment variable:
```
BASE_URL=http://localhost:3333 yarn e2e-tests
```
To follow the tests in the browser while they're running, add the `BROWSER` and `SLOWMO` environment variables:
```
BROWSER=1 SLOWMO=1 yarn e2e-tests
```
## Configure Grafana for development
The default configuration, `grafana.ini`, is located in the `conf` directory.
To override the default configuration, create a `custom.ini` file in the `conf` directory. You only need to add the options you wish to override.
Enable the development mode, by adding the following line in your `custom.ini`:
By now, you should be able to build and test a change you've made to the Grafana source code. In most cases, you need to add at least one data source to verify the change.
Run the `setup.sh` script to setup a set of data sources and dashboards in your local Grafana. The script creates a set of data sources called **gdev-\<type\>**, and a set of dashboards located in a folder called **gdev dashboards**.
Some of the data sources require databases to run in the background.
Installing and configuring databases can be a tricky business. Grafana uses [Docker](https://docker.com) to make the task of setting up databases a little easier. Make sure you [install Docker](https://docs.docker.com/docker-for-mac/install/) before proceeding to the next step.
In the root directory of your Grafana repository, run the following command:
```
make devenv sources=influxdb,loki
```
The script generates a Docker Compose file with the databases you specify as `sources`, and runs them in the background.
See the repository for all the [available data sources](https://github.com/grafana/grafana/tree/master/devenv/docker/blocks). Note that some data sources have specific Docker images for macOS, e.g. `prometheus_mac`.
The resulting image will be tagged as grafana/grafana:dev.
**Note:** If you've already set up a local development environment, and you're running a `linux/amd64` machine, you can speed up building the Docker image:
1. Build the frontend: `go run build.go build-frontend`.
1. Build the Docker image: `make build-docker-dev`.
**Note:** If you are using Docker for macOS, be sure to set the memory limit to be larger than 2 GiB. Otherwise `grunt build` may fail. The memory limit settings are available under **Docker Desktop** -> **Preferences** -> **Advanced**.
Are you having issues with setting up your environment? Here are some tips that might help.
### Too many open files when running `make run`
Depending on your environment, you may have to increase the maximum number of open files allowed.
To see how many open files are allowed, run:
```
ulimit -a
```
To change the number of open files allowed, run:
```
ulimit -S -n 2048
```
The number of files needed may be different on your environment. To determine the number of open files needed by `make run`, run:
```
find ./conf ./pkg ./public/views | wc -l
```
Another alternative is to limit the files being watched. The directories that are watched for changes are listed in the `.bra.toml` file in the root directory.
- Learn how to [Create a pull request](/contribute/pull-request.md).
- Read [How to contribute to Grafana as a junior dev](https://medium.com/@ivanahuckova/how-to-contribute-to-grafana-as-junior-dev-c01fe3064502) by [Ivana Huckova](https://medium.com/@ivanahuckova).
