cdinit: use OverlayFS for root

Signed-off-by: A. Wilcox <AWilcox@Wilcox-Tech.com>

1 files changed, 36 insertions, 13 deletions

diff --git a/cdinit.c b/cdinit.c
index 2990106..44ba094 100644
--- a/cdinit.c
+++ b/cdinit.c
@@ -45,7 +45,7 @@ bool cdi_invoke(const char *command, const char *path, char * const argv[])
 	}
 	else if(our_pid == -1)
 	{
-		fprintf(stdout, "[ !! ] failed to fork: %s\n", strerror(errno));
+		fprintf(stderr, "[ !! ] failed to fork: %s\n", strerror(errno));
 		return false;
 	}
 	else
@@ -55,14 +55,14 @@ bool cdi_invoke(const char *command, const char *path, char * const argv[])
 		waitpid(our_pid, &status, 0);
 		if(!WIFEXITED(status))
 		{
-			fprintf(stdout, "[ !! ] %s caught signal\n", command);
+			fprintf(stderr, "[ !! ] %s caught signal\n", command);
 			return false;
 		}
 
 		code = WEXITSTATUS(status);
 		if(code != 0)
 		{
-			fprintf(stdout, "[ !! ] %s exited with error code %d\n",
+			fprintf(stderr, "[ !! ] %s exited with error code %d\n",
 				command, code);
 			return false;
 		}
@@ -111,8 +111,8 @@ bool cdi_find_media(void)
 	first = udev_enumerate_get_list_entry(dev_list);
 	if(first == NULL)
 	{
-		fprintf(stdout, "No block devices found.\n");
-		fprintf(stdout, "This system cannot boot Adélie Linux "
+		fprintf(stderr, "No block devices found.\n");
+		fprintf(stderr, "This system cannot boot Adélie Linux "
 				"without additional drivers.\n");
 		return false;
 	}
@@ -193,7 +193,7 @@ bool cdi_find_media(void)
 		ioctl(dev_fd, LOOP_SET_FD, squash_fd);
 		close(squash_fd);
 
-		if(mount("/dev/loop4", "/newroot", "squashfs", MS_RDONLY,
+		if(mount("/dev/loop4", "/lowerroot", "squashfs", MS_RDONLY,
 			NULL) != 0)
 		{
 #ifdef DEBUG
@@ -216,7 +216,7 @@ bool cdi_find_media(void)
 	udev_enumerate_unref(dev_list);
 	udev_unref(udev);
 
-	return (access("/newroot/sbin/init", F_OK) == 0);
+	return (access("/lowerroot/sbin/init", F_OK) == 0);
 }
 
 
@@ -237,21 +237,21 @@ int main(void)
 
 	if(mount("none", "/dev", "devtmpfs", 0, NULL) != 0)
 	{
-		fprintf(stdout, "FATAL: Can't mount devtmpfs at /dev: %s\n",
+		fprintf(stderr, "FATAL: Can't mount devtmpfs at /dev: %s\n",
 			strerror(errno));
 		return EXIT_FAILURE;
 	}
 
 	if(mount("none", "/proc", "proc", 0, NULL) != 0)
 	{
-		fprintf(stdout, "FATAL: Can't mount early /proc: %s\n",
+		fprintf(stderr, "FATAL: Can't mount early /proc: %s\n",
 			strerror(errno));
 		return EXIT_FAILURE;
 	}
 
 	if(mount("none", "/sys", "sysfs", 0, NULL) != 0)
 	{
-		fprintf(stdout, "FATAL: Can't mount early /sys: %s\n",
+		fprintf(stderr, "FATAL: Can't mount early /sys: %s\n",
 			strerror(errno));
 		return EXIT_FAILURE;
 	}
@@ -299,7 +299,7 @@ int main(void)
 	 */
 	if(!cdi_find_media())
 	{
-		fprintf(stdout, "FATAL: no boot media found\n");
+		fprintf(stderr, "FATAL: no boot media found\n");
 		return EXIT_FAILURE;
 	}
 
@@ -308,6 +308,29 @@ int main(void)
 		cdi_invoke("clean up", "/sbin/udevadm", argv);
 	}
 
+	/* Create our OverlayFS mount, so everything is writable.
+	 * TODO: USB-based persistence
+	 */
+	if(mount("tmpfs", "/upperroot", "tmpfs", 0, NULL) != 0)
+	{
+		fprintf(stderr, "FATAL: could not mount tmpfs: %s\n",
+			strerror(errno));
+		return EXIT_FAILURE;
+	}
+
+	/* If this fails, we'll find out below */
+	mkdir("/upperroot/.overlay_work", S_IRWXU);
+
+	if(mount("overlay", "/newroot", "overlay", 0,
+		 "lowerdir=/lowerroot,"
+		 "upperdir=/upperroot,"
+		 "workdir=/upperroot/.overlay_work") != 0)
+	{
+		fprintf(stderr, "FATAL: could not mount overlayfs: %s\n",
+			strerror(errno));
+		return EXIT_FAILURE;
+	}
+
 	mount("/dev", "/newroot/dev", NULL, MS_MOVE, NULL);
 	mount("/media", "/newroot/media/live", NULL, MS_MOVE, NULL);
 	mount("/proc", "/newroot/proc", NULL, MS_MOVE, NULL);
@@ -316,7 +339,7 @@ int main(void)
 	chdir("/newroot");
 	if(mount("/newroot", "/", NULL, MS_MOVE, NULL) != 0)
 	{
-		fprintf(stderr, "could not pivot to /newroot: %s\n",
+		fprintf(stderr, "FATAL: could not pivot to /newroot: %s\n",
 			strerror(errno));
 		return EXIT_FAILURE;
 	}
@@ -324,6 +347,6 @@ int main(void)
 	chroot(".");
 	execl("/sbin/init", "init", (char *)0);
 
-	fprintf(stdout, "Going nowhere without my new root's init\n");
+	fprintf(stderr, "Going nowhere without my new root's init\n");
 	return EXIT_FAILURE;
 }