diff --git a/desktop/api.cpp b/desktop/api.cpp
index 649c29e..69c443a 100644
--- a/desktop/api.cpp
+++ b/desktop/api.cpp
@@ -114,13 +114,6 @@ struct EsBundle {
 	ptrdiff_t bytes;
 };
 
-struct SystemStartupDataHeader {
-	// TODO Make mount points and devices equal, somehow?
-	size_t initialMountPointCount;
-	size_t initialDeviceCount;
-	EsHandle themeCursorData;
-};
-
 const EsBundle bundleDefault = {
 	.base = (const BundleHeader *) BUNDLE_FILE_MAP_ADDRESS,
 	.bytes = -1,
diff --git a/desktop/prefix.h b/desktop/prefix.h
index 774ec3a..ad21fb3 100644
--- a/desktop/prefix.h
+++ b/desktop/prefix.h
@@ -337,6 +337,13 @@ struct GlobalData {
 	volatile uint16_t keyboardLayout;
 };
 
+struct SystemStartupDataHeader {
+	// TODO Make mount points and devices equal, somehow?
+	size_t initialMountPointCount;
+	size_t initialDeviceCount;
+	uintptr_t themeCursorData;
+};
+
 #ifdef KERNEL
 #define K_BOOT_DRIVE ""
 #else
diff --git a/kernel/posix.cpp b/kernel/posix.cpp
index 4804b30..b9f2fdb 100644
--- a/kernel/posix.cpp
+++ b/kernel/posix.cpp
@@ -506,15 +506,22 @@ namespace POSIX {
 				EsMemoryCopy(path, (void *) syscall.arguments[0], syscall.arguments[1]);
 
 				Process *process = currentThread->posixData->forkProcess;
-				process->data.environment = ConstantBufferCreate((void *) syscall.arguments[2], syscall.arguments[3], process);
+				process->data.subsystemID = ES_SUBSYSTEM_ID_POSIX;
+				process->data.subsystemData = ConstantBufferCreate((void *) syscall.arguments[2], syscall.arguments[3], process);
 				process->posixForking = true;
 				process->permissions = currentProcess->permissions;
 
-				EsMountPoint mountPoint = {};
+				struct {
+					SystemStartupDataHeader header;
+					EsMountPoint mountPoint;
+				} systemData;
+
+				EsMemoryZero(&systemData, sizeof(systemData));
 				OpenHandleToObject((void *) syscall.arguments[4], KERNEL_OBJECT_NODE, _ES_NODE_DIRECTORY_WRITE);
-				mountPoint.base = process->handleTable.OpenHandle((void *) syscall.arguments[4], _ES_NODE_DIRECTORY_WRITE, KERNEL_OBJECT_NODE);
-				mountPoint.prefixBytes = EsStringFormat(mountPoint.prefix, sizeof(mountPoint.prefix), "|POSIX:");
-				process->data.initialMountPoints = ConstantBufferCreate(&mountPoint, sizeof(EsMountPoint), process);
+				systemData.mountPoint.base = process->handleTable.OpenHandle((void *) syscall.arguments[4], _ES_NODE_DIRECTORY_WRITE, KERNEL_OBJECT_NODE);
+				systemData.mountPoint.prefixBytes = EsStringFormat(systemData.mountPoint.prefix, sizeof(systemData.mountPoint.prefix), "|POSIX:");
+				systemData.header.initialMountPointCount = 1;
+				process->data.systemData = ConstantBufferCreate(&systemData, sizeof(systemData), process);
 
 				// Start the process.
 
@@ -547,8 +554,6 @@ namespace POSIX {
 				currentThread->posixData->forkStack = nullptr;
 				currentThread->posixData->forkUSP = 0;
 
-				if (!process) return -ENOMEM;
-
 				return currentProcess->handleTable.OpenHandle(process, 0, KERNEL_OBJECT_PROCESS);
 			} break;
 
diff --git a/util/build.c b/util/build.c
index 41cc278..ea1d0c5 100644
--- a/util/build.c
+++ b/util/build.c
@@ -1432,6 +1432,38 @@ void DoCommand(const char *l) {
 		printf(ColorNormal);
 	} else if (0 == memcmp(l, "a2l ", 4)) {
 		AddressToLine(l + 3);
+	} else if (0 == strcmp(l, "build-port")) {
+		printf("\nAvailable ports:\n");
+		DIR *directory = opendir("ports");
+		struct dirent *entry;
+
+		while ((entry = readdir(directory))) {
+			char buffer[4096];
+			snprintf(buffer, sizeof(buffer), "ports/%s/port.sh", entry->d_name);
+			FILE *f = fopen(buffer, "rb");
+			
+			if (f) {
+				printf("\t%s\n", entry->d_name);
+				fclose(f);
+			}
+		}
+
+		closedir(directory);
+
+		LoadOptions();
+
+		if (!IsOptionEnabled("Flag.ENABLE_POSIX_SUBSYSTEM")) {
+			printf("\nMost ports require the POSIX subsystem to be enabled.\n");
+			printf("Run " ColorHighlight "config" ColorNormal " and select " ColorHighlight "Flag.ENABLE_POSIX_SUBSYSTEM" ColorNormal " to enable it.\n");
+		}
+
+		printf("\nEnter the port to be built: ");
+		char *l2 = NULL;
+		size_t pos;
+		getline(&l2, &pos, stdin);
+		l2[strlen(l2) - 1] = 0;
+		CallSystemF("ports/%s/port.sh", l2);
+		free(l2);
 	} else if (0 == memcmp(l, "get-source ", 11)) {
 		if (CallSystem("mkdir -p bin/cache && rm -rf bin/source")) {
 			exit(1);