The Raspberry Pi Read-Only SD-card
Download the latest Raspbian Image and load to SD-card
Configure Raspbian to run in read-only mode for increased stability (optional but recommended)
Start by updating the downloaded Raspbian image
sudo apt-get update
sudo apt-get -y upgrade
Then run these commands to make changes to filesystem
sudo cp /etc/default/rcS /etc/default/rcS.orig
sudo sh -c "echo 'RAMTMP=yes' >> /etc/default/rcS"
sudo mv /etc/fstab /etc/fstab.orig
sudo sh -c "echo 'tmpfs /tmp tmpfs nodev,nosuid,size=30M,mode=1777 0 0' >> /etc/fstab"
sudo sh -c "echo 'tmpfs /var/log tmpfs nodev,nosuid,size=30M,mode=1777 0 0' >> /etc/fstab"
sudo sh -c "echo 'proc /proc proc defaults 0 0' >> /etc/fstab"
sudo sh -c "echo '/dev/mmcblk0p1 /boot vfat defaults 0 2' >> /etc/fstab"
sudo sh -c "echo '/dev/mmcblk0p2 / ext4 defaults,ro,noatime,errors=remount-ro 0 1' >> /etc/fstab"
sudo sh -c "echo ' ' >> /etc/fstab"
sudo mv /etc/mtab /etc/mtab.orig
sudo ln -s /proc/self/mounts /etc/mtab
The Pi will now run in Read-Only mode from the next restart.
Before restarting create two shortcut commands to switch between read-only and write access modes.
Firstly “ rpi-rw “ will be the command to unlock the filesystem for editing, run
sudo nano /usr/bin/rpi-rw
and add the following to the blank file that opens
#!/bin/sh
sudo mount -o remount,rw /dev/mmcblk0p2 /
echo "Filesystem is unlocked - Write access"
echo "type ' rpi-ro ' to lock"
save and exit using ctrl-x -> y -> enter and then to make this executable run
sudo chmod +x /usr/bin/rpi-rw
Next “ rpi-ro “ will be the command to lock the filesytem down again, run
sudo nano /usr/bin/rpi-ro
and add the following to the blank file that opens
#!/bin/sh
sudo mount -o remount,ro /dev/mmcblk0p2 /
echo "Filesystem is locked - Read Only access"
echo "type ' rpi-rw ' to unlock"
save and exit using ctrl-x -> y -> enter and then to make this executable run
sudo chmod +x /usr/bin/rpi-ro
Lastly reboot for changes to take effect (note - if serial UART access required make these changes before restarting)
sudo shutdown -r now