I've used Vapor 3, but this is my first time with version 4. I'm setting up a fresh server environment with Ubuntu 20.04 and Swift 5.6.1. I can create a new Swift project, build, and run it just fine without issue.
Next I follow along with Vapor's Install and Getting Started docs. I'm able to install Vapor Toolbox just fine. Then to test I work along with the docs and run:
vapor new hello -n
cd hello
swift run
At first it seems to be working fine, grabbing dependencies:
....
Creating working copy for https://github.com/vapor/async-kit.git
Working copy of https://github.com/vapor/async-kit.git resolved at 1.12.0
Creating working copy for https://github.com/apple/swift-nio-extras.git
Working copy of https://github.com/apple/swift-nio-extras.git resolved at 1.12.0
Building for debugging...
[1605/1613] Wrapping AST for Backtrace for debugging
At that point it exits without an error message or anything.
If I run again it's similar situation. Eventually it spits out an error:
error: emit-module command failed due to signal 9 (use -v to see invocation)
Running verbose spits out a huge and unreadable string of paths and commands.
EDIT: Here's a paste of the verbose output since it's too long to include
It sounds like you're running out of memory. Try enabling swap or giving the machine more RAM and try again