Overview | Read-Only Raspberry Pi
<html> <div class=„row-fluid build-text“ readability=„42“> <p>Most microcontroller projects have an on/off switch or some quick way to cut power, while computers like the Raspberry Pi require an <strong>orderly shutdown</strong> procedure…otherwise the SD card may become <strong>corrupted</strong> and the system will no longer boot.</p> <p>Sometimes just cutting power would be a convenient timesaver, or a system may be left to non-technical users. For installations that don’t require creating or modifying files — such as a dedicated slideshow kiosk — we can configure the operating system to make it <strong>more resistant to unplanned power cuts</strong>.</p> </div> <div class=„row-fluid build-text“ readability=„40“> <p>Linux — or any substantial computer operating system, Windows and Mac are the same way — behind the scenes they’re reading and writing all manner of temporary data to drives (or the SD card with Raspberry Pi). This is why we normally use the <strong>shutdown</strong> command: all those files are put away in a known valid state. But if power is unexpectedly cut, these lingering half-written files can render a card <strong>unbootable</strong>…one can try patching it up, but sometimes there’s no recourse but to <strong>wipe the card and reinstall everything</strong>.</p> </div> <div class=„row-fluid build-text“ readability=„52“> <p>The script we provide here adapts Raspbian to work in a <em><strong>read-only</strong></em> mode. Temporary files are stored in RAM rather than on the SD card, making it more robust in this regard. You can just unplug the system when done. The tradeoff…as the <em>read-only</em> name implies…is that <strong>nothing can be written to the card</strong> in this state. Can’t install software, can’t record pictures. So it’s <em>not</em> the solution to every situation, but may be helpful with certain passive tasks…a <a href=„https://learn.adafruit.com/raspberry-pi-video-looper“>slideshow kiosk</a>, a <a href=„https://learn.adafruit.com/1500-neopixel-led-curtain-with-raspberry-pi-fadecandy“>Fadecandy</a> server, a <a href=„https://learn.adafruit.com/animated-snake-eyes-bonnet-for-raspberry-pi“>Halloween display</a>, etc.</p> <p>Optionally, you can use a jumper or switch to boot the system into normal read/write mode to install new software or data. And, as normal, you still have easy access to the /boot partition if the SD card is mounted on another computer.</p> <p><strong>This guide is based partly on instructions from <a href=„http://petr.io/en/blog/2015/11/09/read-only-raspberry-pi-with-jessie/“>petr.io</a>, which in turn credits <a href=„http://hallard.me/raspberry-pi-read-only/“>Charles Hallard</a> and <a href=„http://k3a.me/how-to-make-raspberrypi-truly-read-only-reliable-and-trouble-free/“>Mario Hros</a>…along with community members’ contributions in those threads and some changes and additions of our own.</strong></p> </div> <div class=„row-fluid build-text“> <ul><li>This <strong>does not work</strong> with the <strong>X11</strong> desktop / PIXEL. It's strictly for <strong>Raspbian Lite </strong>right now. Graphical applications are still possible using SDL, Pygame and so forth, just not X11 at the moment.</li> <li>Setting up read-only mode should be the <strong><em>very last step</em></strong> before deploying a project. Get all your code and data on the system, get software auto-starting as needed, test it normally with the usual boot and shutdown methodology. It’s easier up-front. Once you’re 100% confident in its operation, <em>then</em> use the script.</li> <li> <strong>Back up</strong> the contents of your SD card first. We’ve tested on a couple versions of Raspbian, but maybe something’s changed, or has been overlooked, and could leave the Pi in a weird intermediate state, or the script might break compatibility with some other software.</li> <li>No really, <strong>back up your stuff</strong>.</li> </ul></div> <div class=„row-fluid build-text“ readability=„39“> <p>Pi should be booted and on the network…like mentioned above, everything already configured and fully functional (and backed up) before taking this step.</p> <p><strong>THIS SEQUENCE IS IRREVERSIBLE. We don’t have an uninstall script. There’s an <em>option</em> to boot into read/write mode, but <em>nothing</em> to back out <em>all</em> these changes.</strong></p> <p>From a command line prompt:</p> </div> <div class=„build-code“ readability=„8“> <p> <a href=„https://learn.adafruit.com/read-only-raspberry-pi?view=all#“ class=„code-copy-button“>Copy Code</a> </p> <pre class=„prettyprint linenums“>wget https://raw.githubusercontent.com/adafruit/Raspberry-Pi-Installer-Scripts/master/read-only-fs.sh sudo bash read-only-fs.sh</pre> </div> <div class=„row-fluid build-text“ readability=„33“> <p>The script will repeat all these stern warnings and make you verify at several steps whether to continue. Along the way you’ll be presented with a few options:</p> </div> <div class=„row-fluid build-text“ readability=„33“> <p><strong>Enable boot-time read/write jumper? [y/N]</strong></p> <p>This gives you the option to run the system in read/write mode by inserting a jumper across two pins…</p> </div> <table class=„build-table“ readability=„5“><tr class=„build-row“ readability=„11“><td class=„side-images“> </td> <td class=„side-text“ readability=„34“><div class=„text“ readability=„44“><p>If you answer yes to this question, you’ll also be asked for a <strong>GPIO pin number</strong>. When there’s a jumper between this pin and <strong>ground</strong>, the system will boot into <strong>read/write mode</strong> and you can make changes (but remember to <strong>do a proper shutdown</strong>).</p> <p>Make sure the pin isn’t used by anything else (like if you have a PiTFT display attached). <strong>GPIO21</strong> is easy to remember because it’s right at the end of the header. If you’re using <strong>I2S audio</strong> though, that requires GPIO21 for its own use, so you’ll want to pick another.</p></div></td> </tr></table><div class=„row-fluid build-text“ readability=„40“> <p><strong>Install GPIO-halt utility? [y/N]</strong></p> <p>This installs a utility that initiates a proper shutdown when another GPIO pin is touched to ground.</p> <p>For a read-only system, <strong>you probably don’t need this</strong>…but I’m a little paranoid…or, if you have the system booted in read/write mode, this provides an option if you can’t log in and run a manual shutdown.</p> </div> <table class=„build-table“ readability=„1“><tr class=„build-row“ readability=„3“><td class=„side-images“> <ul><li class=„medium-side“> <a class=„large-side-image-link“ href=„https://learn.adafruit.com/assets/46754“> <img class=„46754-asset medium-side-image img-responsive“ src=„https://cdn-learn.adafruit.com/assets/assets/000/046/754/medium640/raspberry_pi_button.jpg?1506538137“ alt=„raspberry_pi_button.jpg“/></a></li> </ul></td> <td class=„side-text“ readability=„29“><div class=„text“ readability=„33“><p>This likewise will ask for a GPIO pin number. Use the map above. How about GPIO16? It’s right next to a ground pin and we can use one of these button quick-connects.</p></div></td> </tr></table><div class=„row-fluid build-text“ readability=„44“> <p><strong>Enable kernel panic watchdog? [y/N]</strong></p> <p>This option enables software to automatically reboot the system in the event of a kernel panic (a low-level system crash). This is actually pretty rare though, and is not the only way in which programs may crash on the system. You might want to set up your code to auto-restart using <strong>systemd</strong>, but that’s a whole book in itself.</p> <p><em>(The selections here are based on comments in the previously-mentioned blog posts…but in practice the impression I’m getting is that it may be related more to the OS version than the specific hardware. This option might change or be removed in the future.)</em></p> </div> <div class=„row-fluid build-text“ readability=„36“> <p>One last confirmation before the script runs. It may take 5 to 10 minutes, depending on the processor, network and SD card speed. You'll see a few warnings along the way, these can be ignored.</p> </div> <div class=„row-fluid build-text“ readability=„47“> <p><strong>Test</strong> the modified system to make sure that the system boots and your application runs as intended. Try a pass with the read/write jumper and/or the gpio-halt button, if you’ve enabled either of those options.</p> <p><strong>Now make an image of the SD card</strong> (using <em>dd</em> or <em>Apple Pi Baker</em> or whatever your backup tool of preference) and, if it’s a critical application, <strong>burn <em>at least</em> one spare</strong>. There are other ways cards can go bad…static, brown-outs, falling out and getting lost…this read-only setup won’t always save you. SD cards are cheap now! Spares help if you’ve left a system in someone else’s care (let’s say a museum kiosk) and it fails for some reason, you can ask them to just swap out the card until you can get there to troubleshoot. I know at least one Burning Man project rendered useless <em>in the first few minutes</em> of the event because their one and only card fell out and was lost on the playa.</p> </div> <div class=„row-fluid build-text“ readability=„32“> <p>Here's the code 'in line' in case you want to review it here (also, it will print in the PDF)</p> </div> <div class=„build-code“ readability=„97“> <p> <a href=„https://learn.adafruit.com/read-only-raspberry-pi?view=all#“ class=„code-copy-button“>Copy Code</a> </p> <pre class=„prettyprint linenums“>#!/bin/bash # CREDIT TO THESE TUTORIALS: # petr.io/en/blog/2015/11/09/read-only-raspberry-pi-with-jessie # hallard.me/raspberry-pi-read-only # k3a.me/how-to-make-raspberrypi-truly-read-only-reliable-and-trouble-free if [ $(id -u) -ne 0 ]; then
echo "Installer must be run as root." echo "Try 'sudo bash $0'" exit 1
fi clear echo „This script configures a Raspberry Pi“ echo „SD card to boot into read-only mode,“ echo „obviating need for clean shutdown.“ echo „NO FILES ON THE CARD CAN BE CHANGED“ echo „WHEN PI IS BOOTED IN THIS STATE. Either“ echo „the filesystems must be remounted in“ echo „read/write mode, card must be mounted“ echo „R/W on another system, or an optional“ echo „jumper can be used to enable read/write“ echo „on boot.“ echo echo „Links to original tutorials are in“ echo „script source. THIS IS A ONE-WAY“ echo „OPERATION. THERE IS NO SCRIPT TO“ echo „REVERSE THIS SETUP! ALL other system“ echo „config should be complete before using“ echo „this script. MAKE A BACKUP FIRST.“ echo echo „Run time ~5 minutes. Reboot required.“ echo echo -n „CONTINUE? [y/N] “ read if y|Y)$ ; then
echo "Canceled." exit 0
fi # FEATURE PROMPTS ———————————————————- # Installation doesn't begin until after all user input is taken. INSTALL_RW_JUMPER=0 INSTALL_HALT=0 INSTALL_WATCHDOG=0 # Given a list of strings representing options, display each option # preceded by a number (1 to N), display a prompt, check input until # a valid number within the selection range is entered. selectN() {
for ((i=1; i<=$#; i++)); do
echo $i. ${!i}
done
echo
REPLY=""
while :
do
echo -n "SELECT 1-$#: "
read
if [[ $REPLY -ge 1 ]] && [[ $REPLY -le $# ]]; then
return $REPLY
fi
done
} SYS_TYPES=(Pi\ 3\ /\ Pi\ Zero\ W All\ other\ models) WATCHDOG_MODULES=(bcm2835_wdog bcm2708_wdog) OPTION_NAMES=(NO YES) echo -n „Enable boot-time read/write jumper? [y/N] “ read if y|Y)$ ; then
INSTALL_RW_JUMPER=1 echo -n "GPIO pin for R/W jumper: " read RW_PIN=$REPLY
fi echo -n „Install GPIO-halt utility? [y/N] “ read if y|Y)$ ; then
INSTALL_HALT=1 echo -n "GPIO pin for halt button: " read HALT_PIN=$REPLY
fi echo -n „Enable kernel panic watchdog? [y/N] “ read if y|Y)$ ; then
INSTALL_WATCHDOG=1
echo "Target system type:"
selectN "${SYS_TYPES[0]}" \
"${SYS_TYPES[1]}"
WD_TARGET=$?
fi # VERIFY SELECTIONS BEFORE CONTINUING ————————————– echo if [ $INSTALL_RW_JUMPER -eq 1 ]; then
echo "Boot-time R/W jumper: YES (GPIO$RW_PIN)"
else
echo "Boot-time R/W jumper: NO"
fi if [ $INSTALL_HALT -eq 1 ]; then
echo "Install GPIO-halt: YES (GPIO$HALT_PIN)"
else
echo "Install GPIO-halt: NO"
fi if [ $INSTALL_WATCHDOG -eq 1 ]; then
echo "Enable watchdog: YES (${SYS_TYPES[WD_TARGET-1]})"
else
echo "Enable watchdog: NO"
fi echo echo -n „CONTINUE? [y/N] “ read if y|Y)$ ; then
echo "Canceled." exit 0
fi # START INSTALL ———————————————————— # All selections have been validated at this point… # Given a filename, a regex pattern to match and a replacement string: # Replace string if found, else no change. # (# $1 = filename, $2 = pattern to match, $3 = replacement) replace() {
grep $2 $1 >/dev/null if [ $? -eq 0 ]; then # Pattern found; replace in file sed -i "s/$2/$3/g" $1 >/dev/null fi
} # Given a filename, a regex pattern to match and a replacement string: # If found, perform replacement, else append file w/replacement on new line. replaceAppend() {
grep $2 $1 >/dev/null if [ $? -eq 0 ]; then # Pattern found; replace in file sed -i "s/$2/$3/g" $1 >/dev/null else # Not found; append on new line (silently) echo $3 | sudo tee -a $1 >/dev/null fi
} # Given a filename, a regex pattern to match and a string: # If found, no change, else append file with string on new line. append1() {
grep $2 $1 >/dev/null if [ $? -ne 0 ]; then # Not found; append on new line (silently) echo $3 | sudo tee -a $1 >/dev/null fi
} # Given a filename, a regex pattern to match and a string: # If found, no change, else append space + string to last line – # this is used for the single-line /boot/cmdline.txt file. append2() {
grep $2 $1 >/dev/null if [ $? -ne 0 ]; then # Not found; insert in file before EOF sed -i "s/\'/ $3/g" $1 >/dev/null fi
} echo echo „Starting installation…“ echo „Updating package index files…“ apt-get update echo „Removing unwanted packages…“ #apt-get remove -y –force-yes –purge triggerhappy cron logrotate dbus \ # dphys-swapfile xserver-common lightdm fake-hwclock # Let's keep dbus…that includes avahi-daemon, a la 'raspberrypi.local', # also keeping xserver & lightdm for GUI login (WIP, not working yet) apt-get remove -y –force-yes –purge triggerhappy cron logrotate \ dphys-swapfile fake-hwclock apt-get -y –force-yes autoremove –purge # Replace log management with busybox (use logread if needed) echo „Installing busybox-syslogd…“ apt-get -y –force-yes install busybox-syslogd; dpkg –purge rsyslog echo „Configuring system…“ # Install boot-time R/W jumper test if requested GPIOTEST=„gpio -g mode $RW_PIN up\n\ if [ \`gpio -g read $RW_PIN\` -eq 0 ] ; then\n\ \tmount -o remount,rw \/\n\ \tmount -o remount,rw \/boot\n\ fi\n“ if [ $INSTALL_RW_JUMPER -ne 0 ]; then
apt-get install -y --force-yes wiringpi # Check if already present in rc.local: grep "gpio -g read" /etc/rc.local >/dev/null if [ $? -eq 0 ]; then # Already there, but make sure pin is correct: sed -i "s/^.*gpio\ -g\ read.*$/$GPIOTEST/g" /etc/rc.local >/dev/null else # Not there, insert before final 'exit 0' sed -i "s/^exit 0/$GPIOTEST\\nexit 0/g" /etc/rc.local >/dev/null fi
fi # Install watchdog if requested if [ $INSTALL_WATCHDOG -ne 0 ]; then
apt-get install -y --force-yes watchdog
# $MODULE is specific watchdog module name
MODULE=${WATCHDOG_MODULES[($WD_TARGET-1)]}
# Add to /etc/modules, update watchdog config file
append1 /etc/modules $MODULE $MODULE
replace /etc/watchdog.conf "#watchdog-device" "watchdog-device"
replace /etc/watchdog.conf "#max-load-1" "max-load-1"
# Start watchdog at system start and start right away
# Raspbian Stretch needs this package installed first
apt-get install -y --force-yes insserv
insserv watchdog; /etc/init.d/watchdog start
# Additional settings needed on Jessie
append1 /lib/systemd/system/watchdog.service "WantedBy" "WantedBy=multi-user.target"
systemctl enable watchdog
# Set up automatic reboot in sysctl.conf
replaceAppend /etc/sysctl.conf "^.*kernel.panic.*$" "kernel.panic = 10"
fi # Install gpio-halt if requested if [ $INSTALL_HALT -ne 0 ]; then
apt-get install -y --force-yes wiringpi echo "Installing gpio-halt in /usr/local/bin..." cd /tmp curl -LO https://github.com/adafruit/Adafruit-GPIO-Halt/archive/master.zip unzip master.zip cd Adafruit-GPIO-Halt-master make mv gpio-halt /usr/local/bin cd .. rm -rf Adafruit-GPIO-Halt-master # Add gpio-halt to /rc.local: grep gpio-halt /etc/rc.local >/dev/null if [ $? -eq 0 ]; then # gpio-halt already in rc.local, but make sure correct: sed -i "s/^.*gpio-halt.*$/\/usr\/local\/bin\/gpio-halt $HALT_PIN \&/g" /etc/rc.local >/dev/null else # Insert gpio-halt into rc.local before final 'exit 0' sed -i "s/^exit 0/\/usr\/local\/bin\/gpio-halt $HALT_PIN \&\\nexit 0/g" /etc/rc.local >/dev/null fi
fi # Add fastboot, noswap and/or ro to end of /boot/cmdline.txt append2 /boot/cmdline.txt fastboot fastboot append2 /boot/cmdline.txt noswap noswap append2 /boot/cmdline.txt ro^o^t ro # Move /var/spool to /tmp rm -rf /var/spool ln -s /tmp /var/spool # Move /var/lib/lightdm and /var/cache/lightdm to /tmp rm -rf /var/lib/lightdm rm -rf /var/cache/lightdm ln -s /tmp /var/lib/lightdm ln -s /tmp /var/cache/lightdm # Make SSH work replaceAppend /etc/ssh/sshd_config „^.*UsePrivilegeSeparation.*$“ „UsePrivilegeSeparation no“ # bbro method (not working in Jessie?): #rmdir /var/run/sshd #ln -s /tmp /var/run/sshd # Change spool permissions in var.conf (rondie/Margaret fix) replace /usr/lib/tmpfiles.d/var.conf „spool\s*0755“ „spool 1777“ # Move dhcpd.resolv.conf to tmpfs touch /tmp/dhcpcd.resolv.conf rm /etc/resolv.conf ln -s /tmp/dhcpcd.resolv.conf /etc/resolv.conf # Make edits to fstab # make / ro # tmpfs /var/log tmpfs nodev,nosuid 0 0 # tmpfs /var/tmp tmpfs nodev,nosuid 0 0 # tmpfs /tmp tmpfs nodev,nosuid 0 0 replace /etc/fstab „vfat\s*defaults\s“ „vfat defaults,ro “ replace /etc/fstab „ext4\s*defaults,noatime\s“ „ext4 defaults,noatime,ro “ append1 /etc/fstab „/var/log“ „tmpfs /var/log tmpfs nodev,nosuid 0 0“ append1 /etc/fstab „/var/tmp“ „tmpfs /var/tmp tmpfs nodev,nosuid 0 0“ append1 /etc/fstab „\s/tmp“ „tmpfs /tmp tmpfs nodev,nosuid 0 0“ # PROMPT FOR REBOOT ——————————————————– echo „Done.“ echo echo „Settings take effect on next boot.“ echo echo -n „REBOOT NOW? [y/N] “ read if y|Y)$ ; then
echo "Exiting without reboot." exit 0
fi echo „Reboot started…“ reboot exit 0 </pre> </div> </html>
Falls nicht anders bezeichnet, ist der Inhalt dieses Wikis unter der folgenden Lizenz veröffentlicht: CC Attribution-Noncommercial-Share Alike 4.0 International