mutability

- install the two shellscripts into the appropriate places under /etc/initramfs-tools
- run update-initramfs
- put "overlay=yes" on the kernel command line
- reboot

With the overlay in place, the real root is mounted readonly on /ro.
Only the root fs is changed, other filesystems are mounted normally.

Remove "overlay=yes" (or change it to something other than yes) and reboot to go back to readwrite.
(This probably means that you want the commandline config to live somewhere other than on the root fs, e.g. under /boot)

niun

#!/bin/sh
#
#  Read-only Root-FS for Raspian
#
#  Modified 2015 by Pascal Rosin to work on raspian-ua-netinst with
#  overlayfs integrated in Linux Kernel >= 3.18.
#
#  Originally written by Axel Heider (Copyright 2012) for Ubuntu 11.10.
#  This version can be found here:
#  https://help.ubuntu.com/community/aufsRootFileSystemOnUsbFlash#Overlayfs

yeokm1

Read-only FS on Arch Linux ARM

Unlike your typical computer where you usually shutdown properly, I cannot rely on this during the use of my Raspberry Pi. If the Raspberry Pi is improperly shutdown too many times, data corruption in the file system leading to unbootable SD card may result. So we should use a read-only file system.

Full instructions and explanations are obtained from this link but you can run these commands directly. I modified some of the instructions for personal convenience.

Login with default username: alarm, password: alarm

#Optionally enable root over SSH. The rest of these instructions assume u are in root.