diff --git a/logic/net/FileDownload.cpp b/logic/net/FileDownload.cpp
index 239af351..38f0b9c2 100644
--- a/logic/net/FileDownload.cpp
+++ b/logic/net/FileDownload.cpp
@@ -63,6 +63,15 @@ void FileDownload::start()
 	request.setRawHeader(QString("If-None-Match").toLatin1(), m_expected_md5.toLatin1());
 	request.setHeader(QNetworkRequest::UserAgentHeader, "MultiMC/5.0 (Uncached)");
 
+	// Go ahead and try to open the file.
+	// If we don't do this, empty files won't be created, which breaks the updater.
+	// Plus, this way, we don't end up starting a download for a file we can't open.
+	if (!m_output_file.open(QIODevice::WriteOnly))
+	{
+		emit failed(index_within_job);
+		return;
+	}
+
 	auto worker = MMC->qnam();
 	QNetworkReply *rep = worker->get(request);
 
diff --git a/logic/updater/DownloadUpdateTask.cpp b/logic/updater/DownloadUpdateTask.cpp
index fc4d321f..7c5eb84a 100644
--- a/logic/updater/DownloadUpdateTask.cpp
+++ b/logic/updater/DownloadUpdateTask.cpp
@@ -24,6 +24,8 @@
 #include <QTemporaryDir>
 #include <QCryptographicHash>
 
+#include <QDomDocument>
+
 
 DownloadUpdateTask::DownloadUpdateTask(QString repoUrl, int versionId, QObject* parent) :
 	Task(parent)
@@ -197,10 +199,11 @@ void DownloadUpdateTask::parseVersionInfo(VersionInfoFileEnum vfile, VersionFile
 
 		VersionFileEntry file{
 			fileObj.value("Path").toString(),
-			fileObj.value("Executable").toBool(false),
+			fileObj.value("Perms").toVariant().toInt(),
 			FileSourceList(),
 			fileObj.value("MD5").toString(),
 		};
+		QLOG_DEBUG() << "File" << file.path << "with perms" << file.mode;
 		
 		QJsonArray sourceArray = fileObj.value("Sources").toArray();
 		for (QJsonValue val : sourceArray)
@@ -274,7 +277,7 @@ void DownloadUpdateTask::processFileLists()
 					QLOG_DEBUG() << "Will download" << entry.path << "from" << source.url;
 
 					// Download it to updatedir/<filepath>-<md5> where filepath is the file's path with slashes replaced by underscores.
-					QString dlPath = PathCombine(m_updateFilesDir.path(), entry.path.replace("/", "_"));
+					QString dlPath = PathCombine(m_updateFilesDir.path(), QString(entry.path).replace("/", "_"));
 
 					// We need to download the file to the updatefiles folder and add a task to copy it to its install path.
 					FileDownloadPtr download = FileDownload::make(source.url, dlPath);
@@ -283,7 +286,7 @@ void DownloadUpdateTask::processFileLists()
 					netJob->addNetAction(download);
 
 					// Now add a copy operation to our operations list to install the file.
-					m_operationList.append(UpdateOperation::CopyOp(dlPath, entry.path));
+					m_operationList.append(UpdateOperation::CopyOp(dlPath, entry.path, entry.mode));
 				}
 			}
 		}
@@ -300,7 +303,75 @@ void DownloadUpdateTask::processFileLists()
 	m_filesNetJob.reset(netJob);
 	netJob->start();
 
-	// TODO: Write update operations to a file for the update installer.
+	writeInstallScript(m_operationList, PathCombine(m_updateFilesDir.path(), "file_list.xml"));
+}
+
+void DownloadUpdateTask::writeInstallScript(UpdateOperationList& opsList, QString scriptFile)
+{
+	// Build the base structure of the XML document.
+	QDomDocument doc;
+
+	QDomElement root = doc.createElement("update");
+	root.setAttribute("version", "3");
+	doc.appendChild(root);
+
+	QDomElement installFiles = doc.createElement("install");
+	root.appendChild(installFiles);
+
+	QDomElement removeFiles = doc.createElement("uninstall");
+	root.appendChild(removeFiles);
+
+	// Write the operation list to the XML document.
+	for (UpdateOperation op : opsList)
+	{
+		QDomElement file = doc.createElement("file");
+
+		switch (op.type)
+		{
+			case UpdateOperation::OP_COPY:
+				{
+				// Install the file.
+				QDomElement name = doc.createElement("source");
+				QDomElement path = doc.createElement("dest");
+				QDomElement mode = doc.createElement("mode");
+				name.appendChild(doc.createTextNode(op.file));
+				path.appendChild(doc.createTextNode(op.dest));
+				// We need to add a 0 at the beginning here, because Qt doesn't convert to octal correctly.
+				mode.appendChild(doc.createTextNode("0" + QString::number(op.mode, 8)));
+				file.appendChild(name);
+				file.appendChild(path);
+				file.appendChild(mode);
+				installFiles.appendChild(file);
+				QLOG_DEBUG() << "Will install file" << op.file;
+				}
+				break;
+
+			case UpdateOperation::OP_DELETE:
+				{
+				// Delete the file.
+				file.appendChild(doc.createTextNode(op.file));
+				removeFiles.appendChild(file);
+				QLOG_DEBUG() << "Will remove file" << op.file;
+				}
+				break;
+
+			default:
+				QLOG_WARN() << "Can't write update operation of type" << op.type << "to file. Not implemented.";
+				continue;
+		}
+	}
+
+	// Write the XML document to the file.
+	QFile outFile(scriptFile);
+
+	if (outFile.open(QIODevice::WriteOnly))
+	{
+		outFile.write(doc.toByteArray());
+	}
+	else
+	{
+		emitFailed(tr("Failed to write update script file."));
+	}
 }
 
 void DownloadUpdateTask::fileDownloadFinished()
diff --git a/logic/updater/DownloadUpdateTask.h b/logic/updater/DownloadUpdateTask.h
index 6fb745ab..dc30ca15 100644
--- a/logic/updater/DownloadUpdateTask.h
+++ b/logic/updater/DownloadUpdateTask.h
@@ -57,7 +57,7 @@ protected:
 	struct VersionFileEntry
 	{
 		QString path;
-		bool isExecutable;
+		int mode;
 		FileSourceList sources;
 		QString md5;
 	};
@@ -70,9 +70,9 @@ protected:
 	 */
 	struct UpdateOperation
 	{
-		static UpdateOperation CopyOp(QString fsource, QString fdest) { return UpdateOperation{OP_COPY, fsource, fdest, 644}; }
-		static UpdateOperation MoveOp(QString fsource, QString fdest) { return UpdateOperation{OP_MOVE, fsource, fdest, 644}; }
-		static UpdateOperation DeleteOp(QString file) { return UpdateOperation{OP_DELETE, file, "", 644}; }
+		static UpdateOperation CopyOp(QString fsource, QString fdest, int fmode=0644) { return UpdateOperation{OP_COPY, fsource, fdest, fmode}; }
+		static UpdateOperation MoveOp(QString fsource, QString fdest, int fmode=0644) { return UpdateOperation{OP_MOVE, fsource, fdest, fmode}; }
+		static UpdateOperation DeleteOp(QString file) { return UpdateOperation{OP_DELETE, file, "", 0644}; }
 		static UpdateOperation ChmodOp(QString file, int fmode) { return UpdateOperation{OP_CHMOD, file, "", fmode}; }
 
 		//! Specifies the type of operation that this is.
@@ -84,8 +84,8 @@ protected:
 			OP_CHMOD,
 		} type;
 
-		//! The source file. If this is a DELETE or CHMOD operation, this is the file that will be modified.
-		QString source;
+		//! The file to operate on. If this is a DELETE or CHMOD operation, this is the file that will be modified.
+		QString file;
 
 		//! The destination file. If this is a DELETE or CHMOD operation, this field will be ignored.
 		QString dest;
@@ -145,6 +145,11 @@ protected:
 	 */
 	virtual void processFileLists();
 
+	/*!
+	 * Takes the operations list and writes an install script for the updater to the update files directory.
+	 */
+	virtual void writeInstallScript(UpdateOperationList& opsList, QString scriptFile);
+
 	VersionFileList m_downloadList;
 	UpdateOperationList m_operationList;
 
diff --git a/mmc_updater/src/UpdateInstaller.cpp b/mmc_updater/src/UpdateInstaller.cpp
index 23e1a4ca..3ddc1ec0 100644
--- a/mmc_updater/src/UpdateInstaller.cpp
+++ b/mmc_updater/src/UpdateInstaller.cpp
@@ -51,6 +51,11 @@ void UpdateInstaller::setForceElevated(bool elevated)
 	m_forceElevated = elevated;
 }
 
+void UpdateInstaller::setFinishCmd(const std::string& cmd)
+{
+	m_finishCmd = cmd;
+}
+
 std::list<std::string> UpdateInstaller::updaterArgs() const
 {
 	std::list<std::string> args;
@@ -266,7 +271,7 @@ void UpdateInstaller::revert()
 
 void UpdateInstaller::installFile(const UpdateScriptFile& file)
 {
-	std::string destPath = m_installDir + '/' + file.path;
+	std::string destPath = file.dest;
 	std::string target = file.linkTarget;
 
 	// backup the existing file if any
@@ -279,23 +284,15 @@ void UpdateInstaller::installFile(const UpdateScriptFile& file)
 		FileUtils::mkpath(destDir.c_str());
 	}
 
-	if (target.empty())
+	std::string sourceFile = file.source;
+	if (!FileUtils::fileExists(sourceFile.c_str()))
 	{
-		std::string sourceFile = m_packageDir + '/' + FileUtils::fileName(file.path.c_str());
-		if (!FileUtils::fileExists(sourceFile.c_str()))
-		{
-			throw "Source file does not exist: " + sourceFile;
-		}
-		FileUtils::copyFile(sourceFile.c_str(),destPath.c_str());
+		throw "Source file does not exist: " + sourceFile;
+	}
+	FileUtils::copyFile(sourceFile.c_str(),destPath.c_str());
 
-		// set the permissions on the newly extracted file
-		FileUtils::chmod(destPath.c_str(),file.permissions);
-	}
-	else
-	{
-		// create the symlink
-		FileUtils::createSymLink(destPath.c_str(),target.c_str());
-	}
+	// set the permissions on the newly extracted file
+	FileUtils::chmod(destPath.c_str(),file.permissions);
 }
 
 void UpdateInstaller::installFiles()
@@ -391,19 +388,9 @@ void UpdateInstaller::restartMainApp()
 {
 	try
 	{
-		std::string command;
+		std::string command = m_installDir + '/' + m_finishCmd;
 		std::list<std::string> args;
 
-		for (std::vector<UpdateScriptFile>::const_iterator iter = m_script->filesToInstall().begin();
-			iter != m_script->filesToInstall().end();
-			iter++)
-		{
-			if (iter->isMainBinary)
-			{
-				command = m_installDir + '/' + iter->path;
-			}
-		}
-
 		if (!command.empty())
 		{
 			LOG(Info,"Starting main application " + command);
@@ -411,7 +398,7 @@ void UpdateInstaller::restartMainApp()
 		}
 		else
 		{
-			LOG(Error,"No main binary specified in update script");
+			LOG(Error,"No main binary specified");
 		}
 	}
 	catch (const std::exception& ex)
diff --git a/mmc_updater/src/UpdateInstaller.h b/mmc_updater/src/UpdateInstaller.h
index 5dfa263e..1eca0bc7 100644
--- a/mmc_updater/src/UpdateInstaller.h
+++ b/mmc_updater/src/UpdateInstaller.h
@@ -33,6 +33,7 @@ class UpdateInstaller
 		void setWaitPid(PLATFORM_PID pid);
 		void setForceElevated(bool elevated);
 		void setAutoClose(bool autoClose);
+		void setFinishCmd(const std::string& cmd);
 
 		void setObserver(UpdateObserver* observer);
 
@@ -60,6 +61,7 @@ class UpdateInstaller
 		std::string m_installDir;
 		std::string m_packageDir;
 		std::string m_backupDir;
+		std::string m_finishCmd;
 		PLATFORM_PID m_waitPid;
 		UpdateScript* m_script;
 		UpdateObserver* m_observer;
diff --git a/mmc_updater/src/UpdateScript.cpp b/mmc_updater/src/UpdateScript.cpp
index 606163dd..849a2217 100644
--- a/mmc_updater/src/UpdateScript.cpp
+++ b/mmc_updater/src/UpdateScript.cpp
@@ -71,13 +71,14 @@ void UpdateScript::parseUpdate(const TiXmlElement* updateNode)
 UpdateScriptFile UpdateScript::parseFile(const TiXmlElement* element)
 {
 	UpdateScriptFile file;
-	file.path = elementText(element->FirstChildElement("name"));
+	// The name within the update files folder.
+	file.source = elementText(element->FirstChildElement("source"));
+	// The path to install to.
+	file.dest = elementText(element->FirstChildElement("dest"));
 
-	std::string modeString = elementText(element->FirstChildElement("permissions"));
+	std::string modeString = elementText(element->FirstChildElement("mode"));
 	sscanf(modeString.c_str(),"%i",&file.permissions);
 
-	file.linkTarget = elementText(element->FirstChildElement("target"));
-	file.isMainBinary = strToBool(elementText(element->FirstChildElement("is-main-binary")));
 	return file;
 }
 
diff --git a/mmc_updater/src/UpdateScript.h b/mmc_updater/src/UpdateScript.h
index fec463f3..c825e35d 100644
--- a/mmc_updater/src/UpdateScript.h
+++ b/mmc_updater/src/UpdateScript.h
@@ -35,10 +35,12 @@ class UpdateScriptFile
 	public:
 		UpdateScriptFile()
 		: permissions(0)
-		, isMainBinary(false)
 		{}
 
-		std::string path;
+		/// Path to copy from.
+		std::string source;
+		/// The path to copy to.
+		std::string dest;
 		std::string linkTarget;
 
 		/** The permissions for this file, specified
@@ -46,14 +48,11 @@ class UpdateScriptFile
 		  */
 		int permissions;
 
-		bool isMainBinary;
-
 		bool operator==(const UpdateScriptFile& other) const
 		{
-			return path == other.path &&
-			       permissions == other.permissions &&
-			       linkTarget == other.linkTarget &&
-			       isMainBinary == other.isMainBinary;
+			return source == other.source &&
+			       dest == other.dest &&
+			       permissions == other.permissions;
 		}
 };
 
diff --git a/mmc_updater/src/UpdaterOptions.cpp b/mmc_updater/src/UpdaterOptions.cpp
index 1ea820d2..c8f76f6e 100644
--- a/mmc_updater/src/UpdaterOptions.cpp
+++ b/mmc_updater/src/UpdaterOptions.cpp
@@ -111,6 +111,7 @@ void UpdaterOptions::parse(int argc, char** argv)
 	AnyOption parser;
 	parser.setOption("install-dir");
 	parser.setOption("package-dir");
+	parser.setOption("finish-cmd");
 	parser.setOption("script");
 	parser.setOption("wait");
 	parser.setOption("mode");
@@ -140,6 +141,10 @@ void UpdaterOptions::parse(int argc, char** argv)
 	{
 		waitPid = static_cast<PLATFORM_PID>(atoll(parser.getValue("wait")));
 	}
+	if (parser.getValue("finish-cmd"))
+	{
+		finishCmd = parser.getValue("finish-cmd");
+	}
 
 	showVersion = parser.getFlag("version");
 	forceElevated = parser.getFlag("force-elevated");
diff --git a/mmc_updater/src/UpdaterOptions.h b/mmc_updater/src/UpdaterOptions.h
index a8496d9f..b4473a82 100644
--- a/mmc_updater/src/UpdaterOptions.h
+++ b/mmc_updater/src/UpdaterOptions.h
@@ -14,6 +14,7 @@ class UpdaterOptions
 		std::string installDir;
 		std::string packageDir;
 		std::string scriptPath;
+		std::string finishCmd;
 		PLATFORM_PID waitPid;
 		std::string logFile;
 		bool showVersion;
diff --git a/mmc_updater/src/main.cpp b/mmc_updater/src/main.cpp
index e23cf16d..fb072ab5 100644
--- a/mmc_updater/src/main.cpp
+++ b/mmc_updater/src/main.cpp
@@ -137,7 +137,8 @@ int main(int argc, char** argv)
 	         + ", package-dir: " + options.packageDir
 	         + ", wait-pid: " + intToStr(options.waitPid)
 	         + ", script-path: " + options.scriptPath
-	         + ", mode: " + intToStr(options.mode));
+	         + ", mode: " + intToStr(options.mode)
+			 + ", finish-cmd: " + options.finishCmd);
 
 	installer.setMode(options.mode);
 	installer.setInstallDir(options.installDir);
@@ -146,6 +147,7 @@ int main(int argc, char** argv)
 	installer.setWaitPid(options.waitPid);
 	installer.setForceElevated(options.forceElevated);
 	installer.setAutoClose(options.autoClose);
+	installer.setFinishCmd(options.finishCmd);
 
 	if (options.mode == UpdateInstaller::Main)
 	{
diff --git a/mmc_updater/src/tests/TestUpdateScript.cpp b/mmc_updater/src/tests/TestUpdateScript.cpp
index 9e8c1392..30a7572a 100644
--- a/mmc_updater/src/tests/TestUpdateScript.cpp
+++ b/mmc_updater/src/tests/TestUpdateScript.cpp
@@ -18,31 +18,10 @@ void TestUpdateScript::testV2Script()
 	TEST_COMPARE(newFormat.filesToUninstall(),oldFormat.filesToUninstall());
 }
 
-void TestUpdateScript::testPermissions()
-{
-	UpdateScript script;
-	script.parse("file_list.xml");
-
-	for (std::vector<UpdateScriptFile>::const_iterator iter = script.filesToInstall().begin();
-	     iter != script.filesToInstall().end();
-	     iter++)
-	{
-		if (iter->isMainBinary)
-		{
-			TEST_COMPARE(iter->permissions,0755);
-		}
-		if (!iter->linkTarget.empty())
-		{
-			TEST_COMPARE(iter->permissions,0);
-		}
-	}
-}
-
 int main(int,char**)
 {
 	TestList<TestUpdateScript> tests;
 	tests.addTest(&TestUpdateScript::testV2Script);
-	tests.addTest(&TestUpdateScript::testPermissions);
 	return TestUtils::runTest(tests);
 }
 
diff --git a/mmc_updater/src/tests/TestUpdateScript.h b/mmc_updater/src/tests/TestUpdateScript.h
index fd0994fe..513513d5 100644
--- a/mmc_updater/src/tests/TestUpdateScript.h
+++ b/mmc_updater/src/tests/TestUpdateScript.h
@@ -4,6 +4,5 @@ class TestUpdateScript
 {
 	public:
 		void testV2Script();
-		void testPermissions();
 };