configure: Remove --enable-rw-rootfs detect using /etc/fstab instead

This patch removes the --enable-rw-rootfs build flag.  Like OpenRC we
now check /etc/fstab instad; if `/` is listed *and* doesn't have the
`ro` flag set, we remount / read-write.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

configure.ac

@@ -61,10 +61,6 @@ AC_ARG_ENABLE(auto_reload,
         AS_HELP_STRING([--enable-auto-reload], [Automatic reload on any .conf change]),,[
 	enable_auto_reload=no])
 
-AC_ARG_ENABLE(rw-rootfs,
-        AS_HELP_STRING([--enable-rw-rootfs], [Remount / R/W at boot, usually not for embedded]),,[
-	enable_rw_rootfs=no])
-
 AC_ARG_ENABLE(progress,
         AS_HELP_STRING([--enable-progress], [Modern progress display at bootup]),,[
 	enable_progress=no])
@@ -164,9 +160,6 @@ AS_IF([test "x$enable_fallback_shell" = "xyes"], [
 AS_IF([test "x$enable_auto_reload" = "xyes"], [
         AC_DEFINE(AUTO_RELOAD, 1, [Finit automatically does `initctl reload` on any .conf change])])
 
-AS_IF([test "x$enable_rw_rootfs" = "xyes"], [
-        AC_DEFINE(REMOUNT_ROOTFS,  1, [Remount / as rw at boot])])
-
 AS_IF([test "x$enable_progress" = "xyes"], [
         AC_DEFINE(PROGRESS_STYLE, 2, [Modern bootup messages, systemd inspired])])
 
@@ -301,7 +294,6 @@ Optional features:
   Scripting tool logit..: $enable_logit
   Emergency shell.......: $enable_emergency_shell
   Fallback shell........: $enable_fallback_shell
-  Remount / RW at boot..: $enable_rw_rootfs
   Modern progress.......: $enable_progress
   Classic progress......: $enable_progress_classic
   Default console dev...: $console

contrib/alpine/build.sh

@@ -14,7 +14,7 @@ fi
 # The plugins are optional, but you may need D-Bus and X11 if you want
 # to run X-Window, the other configure flags are however required.
 PKG_CONFIG_LIBDIR=/usr/lib/pkgconfig:/usr/local/lib/pkgconfig ./configure	\
-		 --enable-rw-rootfs            --enable-progress		\
+		                               --enable-progress		\
                  --enable-dbus-plugin          --enable-x11-common-plugin	\
 		 --enable-alsa-utils-plugin    --enable-inetd-echo-plugin	\
 		 --enable-inetd-chargen-plugin --enable-inetd-daytime-plugin	\

contrib/debian/build.sh

@@ -22,7 +22,7 @@ echo
 # The plugins are optional, but you may need D-Bus and X11 if you want
 # to run X-Window, the other configure flags are however required.
 ./configure									\
-    --enable-rw-rootfs                --enable-progress				\
+                                      --enable-progress				\
     --enable-dbus-plugin              --enable-x11-common-plugin		\
     --enable-alsa-utils-plugin        --enable-inetd-echo-plugin		\
     --enable-inetd-chargen-plugin     --enable-inetd-daytime-plugin		\

contrib/void/build.sh

@@ -14,7 +14,7 @@ fi
 # The plugins are optional, but you may need D-Bus and X11 if you want
 # to run X-Window, the other configure flags are however required.
 PKG_CONFIG_LIBDIR=/usr/lib/pkgconfig:/usr/local/lib/pkgconfig ./configure	\
-		 --enable-rw-rootfs            --enable-progress		\
+		                               --enable-progress		\
                  --enable-dbus-plugin          --enable-x11-common-plugin	\
 		 --enable-alsa-utils-plugin    --enable-inetd-echo-plugin	\
 		 --enable-inetd-chargen-plugin --enable-inetd-daytime-plugin	\

docs/bootstrap.md

@@ -12,7 +12,7 @@ Bootstrap
 9. Parse `/etc/finit.conf` and all `/etc/finit.d/*.conf` files
 10. Start built-in watchdog, if enabled
 11. Set hostname
-12. Pivot root, or remount `/` read-write, depending on system type
+12. Remount `/` read-write if `/` is listed in `/etc/fstab` without `ro`
 13. Call 1st level hooks, `HOOK_ROOTFS_UP`
 14. Mount all file systems listed in `/etc/fstab` and swap, if available
 15. Enable SysV init signals

docs/build.md

@@ -40,11 +40,6 @@ Below are a few of the main switches to configure:
 
 * `--disable-inetd`: Disable the built-in inetd server.
 
-* `--enable-rw-rootfs`: Most desktop and server systems boot with the
-  root file stystem read-only.  With this setting Finit will remount it
-  as read-write early at boot so the `bootmisc.so` plugin can run.
-  Usually not needed on embedded systems.
-
 * `--enable-static`: Build Finit statically.  The plugins will be
   built-ins (.o files) and all external libraries, except the C library
   will be linked statically.
@@ -73,7 +68,7 @@ First, unpack the archive:
 Then configure, build and install:
 
 ```shell
-    $ ./configure --enable-rw-rootfs            --enable-inetd-echo-plugin        \
+    $ ./configure                               --enable-inetd-echo-plugin        \
                   --enable-inetd-chargen-plugin --enable-inetd-daytime-plugin     \
                   --enable-inetd-discard-plugin --enable-inetd-time-plugin        \
                   --with-heading="Alpine Linux 3.4" --with-hostname=alpine

src/finit.c

@@ -433,7 +433,7 @@ int main(int argc, char *argv[])
 	 */
 	makedir("/dev/shm", 0755);
 	if (!fismnt("/dev/shm") && !ismnt("/etc/fstab", "/dev/shm"))
-		mount("shm", "/dev/shm", "tmpfs", 0, NULL);
+		mount("shm", "/dev/shm", "tmpfs", 0, "mode=0777");
 
 	/*
 	 * New tmpfs based /run for volatile runtime data
@@ -498,10 +498,30 @@ int main(int argc, char *argv[])
 	 * Mount filesystems
 	 */
 	if (!rescue) {
-#ifdef REMOUNT_ROOTFS
-		run("mount -n -o remount,rw /");
-#endif
-#ifdef SYSROOT
+#ifndef SYSROOT
+		/*
+		 * Remount / read-write if it exists in fstab is not 'ro'.
+		 * This is what the Debian sysv initscripts does.
+		 */
+		if (setfsent()) {
+			struct fstab *fs;
+
+			while ((fs = getfsent())) {
+				if (strcmp(fs->fs_file, "/"))
+					continue;
+
+				if (strcmp(fs->fs_type, "ro"))
+					run_interactive("mount -n -o remount,rw /", "Remounting / as read-write");
+				break;
+			}
+
+			endfsent();
+		}
+#else
+		/*
+		 * XXX: Untested, in the initramfs age we should
+		 *      probably use switch_root instead.
+		 */
 		mount(SYSROOT, "/", NULL, MS_MOVE, NULL);
 #endif
 	}