-
-
Save emsi/3c7143f0583566aad14bad182297a104 to your computer and use it in GitHub Desktop.
A scrip to replace the default RPi init to create and chroot to an overlayfs-backed root
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
#!/bin/sh | |
# Read-only Root-FS for Raspian using overlayfs | |
# Version 1.2: | |
# Don't mount ro/rw root inside newroot | |
# Don't remove root from ftab | |
# Move dev & proc to newroot and redirect execed chrooted subshell console to newroot's dev | |
# 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 -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 [ $? -ne 0 ]; then | |
fail "ERROR: could not mount overlayFS" | |
fi | |
# move dev&proc to newroot | |
mount --move /dev /mnt/newroot/dev | |
mount --move /proc /mnt/newroot/proc | |
cd /mnt/newroot | |
pivot_root . mnt | |
exec chroot . sh -c "$(cat <<END | |
# unmount unneeded mounts so we can unmout the old readonly root | |
umount -l -f /mnt | |
umount -l -f /dev | |
umount -l -f /proc | |
# continue with regular init | |
exec /sbin/init | |
END | |
)" <dev/console >dev/console 2>&1 |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment