[Pkg-sysvinit-devel] Re: Drop the mtab magic and just symlink or bindmount /etc/mtab to /lib/init/rw/mtab ?

[Petter Reinholdtsen]

[Petter Reinholdtsen]
> With this in place, it should be safe to let /etc/mtab be a symlink
> to for example /lib/init/rw/mtab, and use mount normally instead of
> with the -n option.

Or just bind-mount it while we boot.  Something like this, completely
untested.

  - Make sure mount /lib/init/rw and /etc/mtab is mounted using mount -n.
  - bind-mount /etc/mtab to /lib/init/rw/mtab, making it writable from
    the very beginning.  Might need to make /etc/mtab~ writable too?
  - umount the bind-mount and copy the content over after the root is
    mounted rw.  We could drop this and just leave it in /lib/init/rw/.

I'm unsure how this would affect selinux.  I am sure it will help us,
as we can drop the mtab.sh script completely, and we can be sure
/etc/mtab include all the content mount wanted to put there.

Index: debian/initscripts/lib/init/mount-functions.sh
===================================================================
--- debian/initscripts/lib/init/mount-functions.sh      (revision 948)
+++ debian/initscripts/lib/init/mount-functions.sh      (working copy)
@@ -110,7 +110,7 @@
        if [ "$VERBOSE" != "no" ]; then
                is_empty_dir "$MTPT" >/dev/null 2>&1 || log_warning_msg "Files undermount point '$MTPT' will be hidden."
        fi
-       mount -n -t $FSTYPE $OPTS $5 $DEVNAME $MTPT
+       mount -t $FSTYPE $OPTS $5 $DEVNAME $MTPT
 }

 #
Index: debian/initscripts/etc/init.d/mountkernfs.sh
===================================================================
--- debian/initscripts/etc/init.d/mountkernfs.sh        (revision 954)
+++ debian/initscripts/etc/init.d/mountkernfs.sh        (working copy)
@@ -22,10 +22,16 @@
        # Get some writable area available before the root is checked
        # and remounted.
        #
-       domount tmpfs "" /lib/init/rw tmpfs -omode=0755,nosuid
+       domount tmpfs "" /lib/init/rw tmpfs "-n -omode=0755,nosuid"
        touch /lib/init/rw/.ramfs

        #
+       # mtab for use while we boot
+       #
+       touch /lib/init/rw/mtab
+       mount -n --bind /lib/init/rw/mtab /etc/mtab
+
+       #
        # Mount proc filesystem on /proc
        #
        domount proc "" /proc proc -onodev,noexec,nosuid
Index: debian/initscripts/etc/init.d/checkroot.sh
===================================================================
--- debian/initscripts/etc/init.d/checkroot.sh  (revision 948)
+++ debian/initscripts/etc/init.d/checkroot.sh  (working copy)
@@ -329,6 +329,9 @@
                mount -n -o remount,$rootopts,$rootmode /
        fi

+       # Remove bind-mount to /lib/init/rw/mtab
+       umount -n /etc/mtab
+
        #
        # We only create/modify /etc/mtab if the location where it is
        # stored is writable. If /etc/mtab is a symlink into /proc/
@@ -342,7 +345,7 @@
          /*)
                if touch "$MTAB_PATH" >/dev/null 2>&1
                then
-                       :> "$MTAB_PATH"
+                       cat /lib/init/rw/mtab > "$MTAB_PATH"
                        rm -f ${MTAB_PATH}~
                        INIT_MTAB_FILE=yes
                fi
Friendly,
-- 
Petter Reinholdtsen