initial commit of the meta-readonly-rootfs-overlay layer

1 files changed, 160 insertions, 0 deletions

diff --git a/recipes-core/initrdscripts/files/init-readonly-rootfs-overlay-boot.sh b/recipes-core/initrdscripts/files/init-readonly-rootfs-overlay-boot.sh
new file mode 100644
index 0000000..315da9b
--- /dev/null
+++ b/recipes-core/initrdscripts/files/init-readonly-rootfs-overlay-boot.sh
@@ -0,0 +1,160 @@
+#!/bin/sh
+
+PATH=/sbin:/bin:/usr/sbin:/usr/bin
+
+ROOT_MOUNT="/rootfs"
+MOUNT="/bin/mount"
+UMOUNT="/bin/umount"
+ROOT_RWDEVICE="tmpfs"
+ROOT_ROMOUNT="/rfs/ro"
+ROOT_RWMOUNT="/rfs/rw"
+
+# Copied from initramfs-framework. The core of this script probably should be
+# turned into initramfs-framework modules to reduce duplication.
+udev_daemon() {
+        OPTIONS="/sbin/udev/udevd /sbin/udevd /lib/udev/udevd /lib/systemd/systemd-udevd"
+
+        for o in $OPTIONS; do
+                if [ -x "$o" ]; then
+                        echo $o
+                        return 0
+                fi
+        done
+
+        return 1
+}
+
+_UDEV_DAEMON=`udev_daemon`
+
+early_setup() {
+    mkdir -p /proc
+    mkdir -p /sys
+    $MOUNT -t proc proc /proc
+    $MOUNT -t sysfs sysfs /sys
+    $MOUNT -t devtmpfs none /dev
+
+    # support modular kernel
+    modprobe isofs 2> /dev/null
+
+    mkdir -p /run
+    mkdir -p /var/run
+
+    $_UDEV_DAEMON --daemon
+    udevadm trigger --action=add
+}
+
+read_args() {
+    [ -z "$CMDLINE" ] && CMDLINE=`cat /proc/cmdline`
+    for arg in $CMDLINE; do
+        optarg=`expr "x$arg" : 'x[^=]*=\(.*\)'`
+        case $arg in
+            root=*)
+                ROOT_DEVICE=$optarg ;;
+            rootfstype=*)
+                modprobe $optarg 2> /dev/null ;;
+            rootrw=*)
+                ROOT_RWDEVICE=$optarg ;;
+            rootrwfstype=*)
+                modprobe $optarg 2> /dev/null ;;
+            video=*)
+                video_mode=$arg ;;
+            vga=*)
+                vga_mode=$arg ;;
+            console=*)
+                if [ -z "${console_params}" ]; then
+                    console_params=$arg
+                else
+                    console_params="$console_params $arg"
+                fi ;;
+        esac
+    done
+}
+
+fatal() {
+    echo $1 >$CONSOLE
+    echo >$CONSOLE
+    exec sh
+}
+
+early_setup
+
+[ -z "$CONSOLE" ] && CONSOLE="/dev/console"
+
+read_args
+
+mount_and_boot() {
+    mkdir -p $ROOT_MOUNT $ROOT_ROMOUNT $ROOT_RWMOUNT
+    mknod /dev/loop0 b 7 0 2>/dev/null
+
+    # Mount read-only root filesystem into initramfs rootfs
+    if ! $MOUNT -o ro,noatime,nodiratime $ROOT_DEVICE $ROOT_ROMOUNT ; then
+        fatal "Could not mount read-only rootfs"
+    fi
+
+    # determine which unification filesystem to use
+    union_fs_type=""
+    if grep -w "overlay" /proc/filesystems; then
+        union_fs_type="overlay"
+    elif grep -w "aufs" /proc/filesystems; then
+        union_fs_type="aufs"
+    else
+        union_fs_type=""
+    fi
+
+    # Build mount options for read write root filesystem.
+    # If no read-write device was specified via kernel commandline, use tmpfs.
+    if [ "tmpfs" == $ROOT_RWDEVICE ]; then
+        ROOT_RWMOUNTOPTIONS="-t tmpfs -o rw,noatime,mode=755"
+    else
+        ROOT_RWMOUNTOPTIONS="-o rw,noatime,mode=755"
+    fi
+
+    # Mount read-write filesystem into initram rootfs
+    if ! $MOUNT $ROOT_RWMOUNTOPTIONS $ROOT_RWDEVICE $ROOT_RWMOUNT ; then
+        fatal "Could not mount read-write rootfs"
+    fi
+
+    # Create/Mount overlay root filesystem 
+    case $union_fs_type in
+        "overlay")
+            mkdir -p $ROOT_RWMOUNT/upperdir $ROOT_RWMOUNT/work
+            $MOUNT -t overlay overlay -o "lowerdir=$ROOT_ROMOUNT,upperdir=$ROOT_RWMOUNT/upperdir,workdir=$ROOT_RWMOUNT/work" $ROOT_MOUNT
+            ;;
+        "aufs")
+            $MOUNT -t aufs -o "dirs=$ROOT_RWMOUNT=rw:$ROOT_ROMOUNT=ro" aufs $ROOT_MOUNT
+            ;;
+        "")
+            fatal "No overlay filesystem type available"
+            ;;
+    esac
+
+    # Move read-only and read-write root filesystem into the overlay filesystem
+    mkdir -p $ROOT_MOUNT/$ROOT_ROMOUNT $ROOT_MOUNT/$ROOT_RWMOUNT
+    $MOUNT --move $ROOT_ROMOUNT $ROOT_MOUNT/$ROOT_ROMOUNT
+    $MOUNT --move $ROOT_RWMOUNT $ROOT_MOUNT/$ROOT_RWMOUNT
+
+    # Watches the udev event queue, and exits if all current events are handled
+    udevadm settle --timeout=3 --quiet
+    # Kills the current udev running processes, which survived after
+    # device node creation events were handled, to avoid unexpected behavior
+    killall -9 "${_UDEV_DAEMON##*/}" 2>/dev/null
+
+    # Move the mount points of some filesystems over to
+    # the corresponding directories under the real root filesystem.
+    for dir in `awk '/\/dev.* \/run\/media/{print $2}' /proc/mounts`; do
+        mkdir -p ${ROOT_MOUNT}/media/${dir##*/}
+        $MOUNT -n --move $dir ${ROOT_MOUNT}/media/${dir##*/}
+    done
+    $MOUNT -n --move /proc ${ROOT_MOUNT}/proc
+    $MOUNT -n --move /sys ${ROOT_MOUNT}/sys
+    $MOUNT -n --move /dev ${ROOT_MOUNT}/dev
+
+    cd $ROOT_MOUNT
+
+    # busybox switch_root supports -c option
+    exec switch_root -c /dev/console $ROOT_MOUNT /sbin/init $CMDLINE ||
+        fatal "Couldn't switch_root, dropping to shell"
+}
+
+mount_and_boot
+