boot/ro-root.sh hinzugefügt

boot/ro-root.sh

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+#!/bin/sh
+
+#  Read-only Root-FS for Raspian using overlayfs
+#  Version 1.1:
+#  Changed to use /proc/mounts rathern than /etc/fstab for deriving the root filesystem.
+#
+#  Version 1:
+#  Created 2017 by Pascal Suter @ DALCO AG, Switzerland to work on Raspian as custom init script
+#  (raspbian does not use an initramfs on boot)
+#
+#  This program is free software: you can redistribute it and/or modify
+#  it under the terms of the GNU General Public License as published by
+#  the Free Software Foundation, either version 3 of the License, or
+#  (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#    You should have received a copy of the GNU General Public License
+#    along with this program.  If not, see
+#    <http://www.gnu.org/licenses/>.
+#
+#
+#  Tested with Raspbian mini, 2017-01-11
+#
+#  This script will mount the root filesystem read-only and overlay it with a temporary tempfs
+#  which is read-write mounted. This is done using the overlayFS which is part of the linux kernel
+#  since version 3.18.
+#  when this script is in use, all changes made to anywhere in the root filesystem mount will be lost
+#  upon reboot of the system. The SD card will only be accessed as read-only drive, which significantly
+#  helps to prolong its life and prevent filesystem coruption in environments where the system is usually
+#  not shut down properly
+#
+#  Install:
+#  copy this script to /sbin/overlayRoot.sh and add "init=/sbin/overlayRoot.sh" to the cmdline.txt
+#  file in the raspbian image's boot partition.
+#  I strongly recommend to disable swapping before using this. it will work with swap but that just does
+#  not make sens as the swap file will be stored in the tempfs which again resides in the ram.
+#  run these commands on the booted raspberry pi BEFORE you set the init=/sbin/overlayRoot.sh boot option:
+#  sudo dphys-swapfile swapoff
+#  sudo dphys-swapfile uninstall
+#  sudo update-rc.d dphys-swapfile remove
+#
+#  To install software, run upgrades and do other changes to the raspberry setup, simply remove the init=
+#  entry from the cmdline.txt file and reboot, make the changes, add the init= entry and reboot once more.
+
+fail(){
+        echo -e "$1"
+        /bin/bash
+}
+
+# load module
+modprobe overlay
+if [ $? -ne 0 ]; then
+    fail "ERROR: missing overlay kernel module"
+fi
+# mount /proc
+mount -t proc proc /proc
+
+# create a writable fs to then create our mountpoints
+mount -t tmpfs inittemp /mnt
+if [ $? -ne 0 ]; then
+    fail "ERROR: could not create a temporary filesystem to mount the base filesystems for overlayfs"
+fi
+mkdir /mnt/lower
+mkdir /mnt/rw
+mount -t tmpfs root-rw /mnt/rw
+if [ $? -ne 0 ]; then
+    fail "ERROR: could not create tempfs for upper filesystem"
+fi
+mkdir /mnt/rw/upper
+mkdir /mnt/rw/work
+mkdir /mnt/newroot
+
+# mount root filesystem readonly
+rootDev=`awk '$2 == "/" {print $1}' /proc/mounts`
+rootMountOpt=`awk '$2 == "/" {print $4}' /proc/mounts`
+rootFsType=`awk '$2 == "/" {print $3}' /proc/mounts`
+mount -t ${rootFsType} -o ${rootMountOpt},ro ${rootDev} /mnt/lower
+if [ $? -ne 0 ]; then
+    fail "ERROR: could not ro-mount original root partition"
+fi
+mount -t overlay -o lowerdir=/mnt/lower,upperdir=/mnt/rw/upper,workdir=/mnt/rw/work overlayfs-root /mnt/newroot
+if [ $? -ne 0 ]; then
+    fail "ERROR: could not mount overlayFS"
+fi
+# create mountpoints inside the new root filesystem-overlay
+mkdir /mnt/newroot/ro
+mkdir /mnt/newroot/rw
+# remove root mount from fstab (this is already a non-permanent modification)
+grep -v "$rootDev" /mnt/lower/etc/fstab > /mnt/newroot/etc/fstab
+echo "#the original root mount has been removed by overlayRoot.sh" >> /mnt/newroot/etc/fstab
+echo "#this is only a temporary modification, the original fstab" >> /mnt/newroot/etc/fstab
+echo "#stored on the disk can be found in /ro/etc/fstab" >> /mnt/newroot/etc/fstab
+# change to the new overlay root
+cd /mnt/newroot
+pivot_root . mnt
+exec chroot . sh -c "$(cat <<END
+# move ro and rw mounts to the new root
+mount --move /mnt/mnt/lower/ /ro
+if [ $? -ne 0 ]; then
+    echo "ERROR: could not move ro-root into newroot"
+    /bin/bash
+fi
+mount --move /mnt/mnt/rw /rw
+if [ $? -ne 0 ]; then
+    echo "ERROR: could not move tempfs rw mount into newroot"
+    /bin/bash
+fi
+# unmount unneeded mounts so we can unmout the old readonly root
+umount /mnt/mnt
+umount /mnt/proc
+umount -l -f /mnt/dev
+umount -l -f /mnt
+# continue with regular init
+exec /sbin/init
+END
+)"