The Problem

As my family frequently reminds me, most of my tech problems are of my own making.

For instance, I wanted to play Civilization 5 with a friend of mine through Steam. I have a Linux/Windows dual-boot with a shared NTFS partition so that I can share files between the operating systems. I run Linux by default. I also have Hibernate disabled on Windows because I can't use the shared partition from Linux if Windows is hibernated - Windows doesn't see the new changes.

This led to a perfect storm of interactions, since running Civ required

  • Rebooting the machine
  • Waiting about 10 minutes for Windows to cold-start from a HDD (remember that Hibernate is disabled)
  • Waiting another 5-10 minutes for Steam and Civ to launch

Needless to say, this was frustrating for both my friend and I.

Trying new things

I found recently that Steam has a compatibility layer for playing Windows games from other OSs. I downloaded it and gave it a try on a single-player game. It works great, I have no complaints.

The first time I tried to play with my friend, though, I got repeated issues saying 'Could not connect to host'. Related, I block outgoing network traffic by default at the firewall level. Unfortunately, Civ uses random ports to connect, so I can't whitelist it like I do for HTTP, SSH, etc. My normal solution here is to have a group called internet which is whitelisted by IPTables (the native firewall software on Linux, similar to Windows Firewall). If I want to, for example, chat via Discord, I run sg internet discord which allows unrestricted network traffic for that single Discord instance.

When I tried this with Steam, however, I ran into all sorts of strange errors. Sometimes Civ would launch but show network errors when I tried to connect. Sometimes Steam wouldn't recognize my game library, mounted on the NTFS partition so I don't have to redownload 5 GB of assets when I reboot. I tried re-adding the library but got the message 'The partition where the game library is mounted must allow programs to be executed'. This was exceedingly odd because I execute programs on that partition all the time.

Strange and Maddening Rules

I finally tracked the error down to Steam trying to create and run a shell script unsuccessfully. Fun fact: strings shows, among other things, a complete shell script:

exit 0
Couldn't write %s: %s

The issue was that my NTFS drive only recognized me, UID 1000 and GID 1000, as a user. Any file written by any other user or group would have the ownership set to root:root. Worse yet, the OS would then deny all permissions to you (since you're not root).

I spent about a half hour reading through lots of manuals about Linux <=> Windows permissions (here's the manual if you're looking for it). The solution I came up with was to explicitly add the internet group as me in <mountpoint>/.NTFS-3G/UserMapping.

Now everything works!

Even more info