How to verify file existence in image?

To verify the existence of a file in a Docker image, you can follow these steps:

Run a container from the image: Start a container using the image you want to check.
```
docker run --name temp-container -d my-nginx-image
```
Access the container's shell: Use docker exec to open a shell in the running container.
```
docker exec -it temp-container /bin/bash
```
(Use /bin/sh if the image does not have bash.)
Check for the file: Once inside the container, you can use the ls command to check if the file exists.
```
ls /usr/share/nginx/html/index.html
```
Exit the container: After verifying, you can exit the shell.
```
exit
```
Remove the temporary container: If you no longer need the container, you can remove it.
```
docker rm -f temp-container
```

This process will confirm whether the specified file exists in the image.