Actual override script for RO FS added
This commit is contained in:
Milan Toman
53
overlay.sh
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53
overlay.sh
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#/etc/initramfs-tools/scripts/overlay
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# Local filesystem mounting -*- shell-script -*-
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#
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# This script overrides local_mount_root() in /scripts/local
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# and mounts root as a read-only filesystem with a temporary (rw)
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# overlay filesystem.
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#
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. /scripts/local
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local_mount_root()
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{
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local_top
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local_device_setup "${ROOT}" "root file system"
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ROOT="${DEV}"
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# Get the root filesystem type if not set
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if [ -z "${ROOTFSTYPE}" ]; then
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FSTYPE=$(get_fstype "${ROOT}")
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else
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FSTYPE=${ROOTFSTYPE}
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fi
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local_premount
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# CHANGES TO THE ORIGINAL FUNCTION BEGIN HERE
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# N.B. this code still lacks error checking
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modprobe ${FSTYPE}
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checkfs ${ROOT} root "${FSTYPE}"
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# Create directories for root and the overlay
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mkdir /lower /upper
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# Mount read-only root to /lower
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if [ "${FSTYPE}" != "unknown" ]; then
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mount -r -t ${FSTYPE} ${ROOTFLAGS} ${ROOT} /lower
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else
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mount -r ${ROOTFLAGS} ${ROOT} /lower
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fi
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modprobe overlay || insmod "/lower/lib/modules/$(uname -r)/kernel/fs/overlayfs/overlay.ko"
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# Mount a tmpfs for the overlay in /upper
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mount -t tmpfs tmpfs /upper
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mkdir /upper/data /upper/work
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# Mount the final overlay-root in $rootmnt
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mount -t overlay \
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-olowerdir=/lower,upperdir=/upper/data,workdir=/upper/work \
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overlay ${rootmnt}
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}
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119
overlayRoot.sh
119
overlayRoot.sh
@@ -1,119 +0,0 @@
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#!/bin/sh
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# Read-only Root-FS for Raspian using overlayfs
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# Version 1.0
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#
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# Created 2017 by Pascal Suter @ DALCO AG, Switzerland to work on Raspian as custom init script
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# (raspbian does not use an initramfs on boot)
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see
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# <http://www.gnu.org/licenses/>.
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#
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#
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# Tested with Raspbian mini, 2017-01-11
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#
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# This script will mount the root filesystem read-only and overlay it with a temporary tempfs
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# which is read-write mounted. This is done using the overlayFS which is part of the linux kernel
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# since version 3.18.
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# when this script is in use, all changes made to anywhere in the root filesystem mount will be lost
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# upon reboot of the system. The SD card will only be accessed as read-only drive, which significantly
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# helps to prolong its life and prevent filesystem coruption in environments where the system is usually
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# not shut down properly
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#
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# Install:
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# copy this script to /sbin/overlayRoot.sh and add "init=/sbin/overlayRoot.sh" to the cmdline.txt
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# file in the raspbian image's boot partition.
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# I strongly recommend to disable swapping before using this. it will work with swap but that just does
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# not make sens as the swap file will be stored in the tempfs which again resides in the ram.
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# run these commands on the booted raspberry pi BEFORE you set the init=/sbin/overlayRoot.sh boot option:
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# sudo dphys-swapfile swapoff
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# sudo dphys-swapfile uninstall
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# sudo update-rc.d dphys-swapfile remove
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#
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# To install software, run upgrades and do other changes to the raspberry setup, simply remove the init=
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# entry from the cmdline.txt file and reboot, make the changes, add the init= entry and reboot once more.
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fail(){
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echo -e "$1"
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/bin/bash
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}
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# load module
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modprobe overlay
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if [ $? -ne 0 ]; then
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fail "ERROR: missing overlay kernel module"
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fi
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# mount /proc
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mount -t proc proc /proc
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if [ $? -ne 0 ]; then
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fail "ERROR: could not mount proc"
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fi
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# create a writable fs to then create our mountpoints
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mount -t tmpfs inittemp /mnt
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if [ $? -ne 0 ]; then
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fail "ERROR: could not create a temporary filesystem to mount the base filesystems for overlayfs"
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fi
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mkdir /mnt/lower
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mkdir /mnt/rw
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mount -t tmpfs root-rw /mnt/rw
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if [ $? -ne 0 ]; then
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fail "ERROR: could not create tempfs for upper filesystem"
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fi
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mkdir /mnt/rw/upper
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mkdir /mnt/rw/work
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mkdir /mnt/newroot
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# mount root filesystem readonly
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rootDev=/dev/mmcblk0p2
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rootPARTUUID=`awk '$2 == "/" {print $1}' /etc/fstab`
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rootMountOpt=`awk '$2 == "/" {print $4}' /etc/fstab`
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rootFsType=`awk '$2 == "/" {print $3}' /etc/fstab`
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mount -t ${rootFsType} -o ${rootMountOpt},ro ${rootDev} /mnt/lower
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if [ $? -ne 0 ]; then
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fail "ERROR: could not ro-mount original root partition"
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fi
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mount -t overlay -o lowerdir=/mnt/lower,upperdir=/mnt/rw/upper,workdir=/mnt/rw/work overlayfs-root /mnt/newroot
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if [ $? -ne 0 ]; then
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fail "ERROR: could not mount overlayFS"
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fi
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# create mountpoints inside the new root filesystem-overlay
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mkdir /mnt/newroot/ro
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mkdir /mnt/newroot/rw
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# remove root mount from fstab (this is already a non-permanent modification)
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grep -v "$rootPARTUUID" /mnt/lower/etc/fstab > /mnt/newroot/etc/fstab
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echo "#the original root mount has been removed by overlayRoot.sh" >> /mnt/newroot/etc/fstab
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echo "#this is only a temporary modification, the original fstab" >> /mnt/newroot/etc/fstab
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echo "#stored on the disk can be found in /ro/etc/fstab" >> /mnt/newroot/etc/fstab
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# change to the new overlay root
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cd /mnt/newroot
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pivot_root . mnt
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exec chroot . sh -c "$(cat <<END
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# move ro and rw mounts to the new root
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mount --move /mnt/mnt/lower/ /ro
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if [ $? -ne 0 ]; then
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echo "ERROR: could not move ro-root into newroot"
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/bin/bash
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fi
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mount --move /mnt/mnt/rw /rw
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if [ $? -ne 0 ]; then
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echo "ERROR: could not move tempfs rw mount into newroot"
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/bin/bash
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fi
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# unmount unneeded mounts so we can unmout the old readonly root
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umount /mnt/mnt
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umount /mnt/proc
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umount /mnt/dev
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umount /mnt
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# continue with regular init
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exec /sbin/init
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END
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)"
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