Read-only root filesystem on Raspbian
While running Raspbian on my Raspberry Pi (Model B), the SD card repeatedly got corrupted when I removed the +5V power without properly halting the system.
The easiest solution was to make everything read-only from boot time.
I did that by modifying /etc/fstab:
proc /proc proc defaults 0 0 /dev/mmcblk0p1 /boot vfat defaults,ro 0 2 /dev/mmcblk0p2 / ext4 defaults,noatime,ro 0 1
The drawbacks:
- Of course, you can’t write to files or create new files.
- You can’t setup new applications.
- Log files and the lock files of some processes are not written at all.
However, the system seems to work at all. Luckily, you can easily remount a read-only filesystem in read-write mode, e. g. if you want to do some development.
Warning! The code below is only an example, you should check how your system is partitioned.
/usr/bin/pi-rw:
#!/bin/bash
sudo mount -n -o remount,rw,defaults /dev/mmcblk0p1 /boot
sudo mount -n -o remount,rw,defaults,noatime /dev/mmcblk0p2 /
So my Pi starts in read-only mode, and if I want to switch to read-write mode I execute:
pi-rw
If I want to change back to read-only mode, I reboot the system - as some processes always hold the root partition, you can check that by typing:
fuser -vm /
I feel that it’s a quick and dirty fix for the problem, some more sophisticated solutions may exist. One example is IPE, a blackout-proof flavor or Raspbian.
The source of this post is my previous blog at HA5KFU.