Probably not a surprise, given how it works, but I thought someone should report this. It would be by far most useful server-side, and as it stands I'm not sure it could work on a headless server at all.
Anyway, the --help output ought to document this.
Crash report: http://sprunge.us/aKiS
--generate-map-preview crashes on the headless server
Re: --generate-map-preview crashes on the headless server
Yeah that's not a public feature yet - it was just added for some development work 
Also it will never work on the headless instance because the headless instance doesn't support graphics and can't generate an image without them.
Also it will never work on the headless instance because the headless instance doesn't support graphics and can't generate an image without them.
If you want to get ahold of me I'm almost always on Discord.
Re: --generate-map-preview crashes on the headless server
That's what I figured. It's a pity; it'd be a really useful feature. Actually...
Before I dive into writing a dynmap-like mod (using an external server), do you know if it's possible for mods to write arbitrary binary data to <some file>? It's fine if that's limited to a single directory, or even a single file, but I don't feel like trying to shove the entire map through the console output.
Before I dive into writing a dynmap-like mod (using an external server), do you know if it's possible for mods to write arbitrary binary data to <some file>? It's fine if that's limited to a single directory, or even a single file, but I don't feel like trying to shove the entire map through the console output.