Renaming a file on Debian Wheezy does not work using fs.rename or fs.renameSync.
This only happens in files moved from /tmp/ to another location.
The reporte
This is another solution that works for me:
var fs = require("fs"),
util = require('util');
...
//fs.renameSync(files.upload.path, "/tmp/test.png");
var readStream = fs.createReadStream(files.upload.path)
var writeStream = fs.createWriteStream("/tmp/test.png");
util.pump(readStream, writeStream, function() {
fs.unlinkSync(files.upload.path);
});