Comment by Stan Chang Khin Boon (JIRA)

I do have similar issue on ubuntu 14.04. This is intermittent. Some user reported having it working and some don't.

I had experience both working (on my MBP) and non working case (on digital ocean).

The following repository is the Dockerfile that can hopefully recreate the environment.

https://github.com/lxcid/docker-swift

Please use 2.2 as master is attempting to try to build from source.

Comment by Stan Chang Khin Boon (JIRA)

If you are using Docker, run your container with --privileged=true will fix the issue. Not ideal but at least we know that its related to permissions.

Comment by Stan Chang Khin Boon (JIRA)

The solution is discovered here: apple/swift-docker#9 (comment)

From docker's documentation at https://docs.docker.com/engine/reference/commandline/run/#full-container-capabilities-privileged

… by default, most potentially dangerous kernel capabilities are dropped; … However, the --privileged flag will allow it to run

It seems that the REPL requires some kernel level capabilities. Is this something we can avoid?

Comment by Kito (JIRA)

Thanks Stan. Confirmed that running privileged works around the issue.

I'm going to continue debugging to see if there is a more permanent solution.

Comment by Kate Stone (JIRA)

The REPL is actually a special case of the Swift debugger for reasons elaborated on here, so kernel privileges associated with debugging processes are definitely required.

Comment by Kate Stone (JIRA)

Works as expected. Debugging privileges are required for the REPL.

Comment by Kate Stone (JIRA)

I've edited the title to better reflect the presumed nature of the issue and have resolved it per my comment above. Go ahead and re-open if this turns out not to be an accurate assessment.

Could we get a better diagnostic here? The current error is

error: failed to launch REPL process: process launch failed: 'A' packet returned an error: 8

Maybe something about lacking privileges? The issue here is not clear at all from the error message.

Comment by Timothy S Hawkins (JIRA)

This is the same issue you get when trying to run Swift on the "Ubuntu on windows" subsystem on windows 10. However there is no opportunity to change the kernel permissions on this version.