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How to make RaspberryPi truly read-only, reliable and trouble-free

December 4th, 2014 Leave a comment Go to comments

RaspberryPi is a nice, small device which can be used for various automation purposes, internet of things or as an advanced camera. I have been using 5 RPis as a camera with motion detection and post-processing. This application requires high reliability and it was a pretty long journey until all the issues were solved. Here I am writing the most important things I have learned so you don’t need to go through the same stuff again (my cameras were placed on a remote location, making the whole process more complicated).

(Please don’t mind my English mistakes, I wrote this article in a hurry, haven’t even re-read it myself yet.)

1. Connectivity

1.2 Power

A good power is the first important requirement! Make sure you use a reliable power supply with enough power – I found the best power supply to be the one from iPad 1/2. Non-name cheap chinese adapters may work for some time but will fail in couple of years due to bad caps or overall bad design.

Don’t forget to check the cable. Dead-cheap cables with “100% copper” from Aliexpress can sometimes work for data transfer but can’t transfer enough power. The thinner the cable is, the higher voltage drop it will cause on higher power draw. There are many calculators online which can compute the voltage drop for you. Raspberry needs at least 4.65V all the time. The closer to the 5V, the better.

Lower or unstable voltage can cause great variety of “strange” behavior, including random reboots.

1.2 Wifi

Of course, the first thing you need is proper connectivity, especially if you have your RPi on a remote location. This seemed easy – just use wifi dongle, set up wpa_supplicant and all done. No. There are many wifi dongles and most of them are very bad (poor signal quality). If you don’t have super-good signal on the site, definitely buy a dongle with external antenna! Next.. firmwares can be old, making frequent disconnections, or power saving enabled, see my response here http://raspberrypi.stackexchange.com/a/17179. It’s worth setting up a wifi checking script. This works for me – https://paste.k3a.me/view/449a6f1c .

I have a great success with older Atheros AR9271 – it is also well-supported by Linux. I am still using it and would buy it again.

2. Remote shell

Related to the Connectivity. You need to be able to connect there remotely. I set up SSH tunnel (reverse port forwarding) because none of the RPis had a public IP address. Here is the script (/usr/local/bin/sshtunnel.sh) https://paste.k3a.me/view/a7e07bb1. Rc-script for it is here (/etc/init.d/sshtunnel) https://paste.k3a.me/view/7d74f0ae. All RC scripts must be writable so make sure to do ‘chmod a+x script’ on them. It is just for an inspiration, you need to edit it for your setup. Basically after boot or wifi re-connection, RPi connects to my server and starts reverse-port-forwarding so I can access RPi from my server. RPi logs in to the server using a separate account and using SSH keys (so without a password) you can look up the relevant info online/google. I suggest you to set up SSH login from the RPi too so you can log to RPi from the server without password. That improves life a lot.

3. Bad SD card

To survive an unexpected poweroff, you need to have all filesystem mounted read-only (more about it later). But first… even if you have your FS read-only, a cheap SD card can destroy the data on the card itself. So I suggest you buy a more reliable SD card, ideally check http://elinux.org/RPi_SD_cards

4. Read-only filesystem (older SysV-based Raspian)

This is one of the most complicated things but when done properly, it’s not too much work and it won’t cause any problems.

Unless you have special requirements, there are only a few paths which needs to be writable. So let’s go through all steps required to make a truly, trouble-free read-only RPi:

4.1 Update your RPi so you have the recent software

It’s a bad idea to set it up with an old software. That may complicate the update later…

4.2 Remove unnecessary services and files

Here is the command. Of course, remove only what you don’t need. But this is what you probably won’t need on a headless RPi. You definitely don’t want cron on your read-only RPi unless you have external hardware clock source, more about it later.

apt-get remove --purge wolfram-engine triggerhappy cron anacron logrotate dbus dphys-swapfile xserver-common lightdm fake-hwclock
insserv -r x11-common
apt-get autoremove --purge

4.3 Install buysbox syslog

You won’t need normal syslog text files on a read-only filesystem, either. Install busybox syslog instad. It logs into memory and is very lightweight. You can then use logread command to read syslog ringbuffer from the memory when needed.

apt-get install busybox-syslogd
dpkg --purge rsyslog

4.4 Disable filesystem check and swap

Because the filesystem will be mounted read-only, there is nothing to be corrupted so filesystem check must be disabled. I say MUST because it MUST. If you don’t have an external HW clock and use NTP time sync only and you do a change to the filesystem and reboot, filesystem check will see it as an update from the future, denying further boot, requiring manual action on the site. To disable filesystem checks, specifying ‘fastboot’ to the kernel cmdline should be enough. You also don’t want any swapfiles. You can disable them by specifying ‘noswap’ to the cmdline. So edit /boot/cmdline.txt and append the following two at the end of the line:

fastboot noswap

You may need  to replace fsck.repair=yes with fsck.mode=skip.

4.5 Set up clock sync.

Because you uninstalled fake-hwclock (it won’t be able to store clock on a readonly filesystem), you need to install and set up NTP sync. Also clock keeping is poor on a standard RPi so you may consider updating time regularly (every hour or two should be enough).

I used ntpdate for this. apt-get install ntpdate. I added it to /etc/rc.local:

/usr/sbin/ntpdate -b cz.pool.ntp.org # change the ntp server according to your location

4.6 Update some writable paths

Now you need to update a few services which writes something. wpa_supplicant for WiFi is ok as it already writes to /tmp. DHCP lease is the major problem. Simple solution is to delete the old directory and make it as a symlink to tmp like this:

rm -rf /var/lib/dhcp/
ln -s /tmp /var/lib/dhcp

You can consider adding more symlinks from some /var subdirectories, especially run,spool and lock
rm -rf /var/run /var/spool /var/lock
ln -s /tmp /var/run 
ln -s /tmp /var/spool
ln -s /tmp /var/lock

Note that boot scripts may do chmod of /var/spool to 755, therefore making the whole /tmp 755. If that happens to you, consider not using the symlink for /var/spool and add a new tmpfs row to /etc/fstab to create a new temporary mount for /var/spool separately.  (thanks Martin).

4.7 Consider disabling some other startup scripts

insserv -r bootlogs
insserv -r sudo # if you plan to be root all the time
insserv -r alsa-utils # if you don't need alsa stuff (sound output)
insserv -r console-setup
insserv -r fake-hwclock # probably already removed at this point..

If you use alsamixer to set up volume level, make sure to do so in read-write filesystem. If won’t be able to store it on a readonly filesystem. It normally uses this path /var/lib/alsa/asound.state .

4.8 Tell the kernel to mount root filesystem read-only!

Finally getting there.. Add ” ro” at the end of your  /boot/cmdline.txt line.

4.9. Add “,ro” flag to both block devices in /etc/fstab

…to let the system know you want to mount them read-only:

proc              /proc           proc    defaults     0       0
/dev/mmcblk0p1    /boot           vfat    defaults,ro  0       2
/dev/mmcblk0p2    /               ext4    defaults,ro  0       1
tmpfs             /tmp            tmpfs   defaults     0       0

4. Read-only filesystem (SystemD-based newer Raspian)

4.1 Relocate some paths which need write access

mv /etc/resolv.conf /var/run/resolv.conf && ln -s /var/run/resolv.conf /etc/resolv.conf
mv /var/lib/dhcp /var/run/dhcp && ln -s /var/run/dhcp /var/lib/dhcp
rm -rf /var/lib/dhcpcd5 && ln -s /var/run /var/lib/dhcpcd5
rm -rf /var/db && mkdir -p /var/run/db && ln -s /var/run/db /var/db

4.2 Stop and mask  SystemD timers and services which won’t work on read-only machine

systemctl stop systemd-tmpfiles-clean.timer apt-daily.timer apt-daily-upgrade.timer
systemctl disable systemd-tmpfiles-clean.timer systemd-tmpfiles-clean apt-daily.timer apt-daily-upgrade.timer
systemctl disable dphys-swapfile && rm /var/swap
systemctl disable bluetooth cron
systemctl mask systemd-update-utmp systemd-update-utmp-runlevel systemd-rfkill systemd-rfkill.socket

Notice that I disabled bluetooth as I don’t need it. You should be able to get it work eventually but I haven’t tested and disabled it.

4.3 Remove unnecessary software

apt-get remove -y avahi-daemon triggerhappy bluez
apt-get autoremove -y

Avahi daemon is for mDNS to auto-discover services on the same network – you can eventually get it work if you need it but most people don’t need it and it probably needs write access somewhere.

Triggerhappy is hotkey daemon which is useless on headless sytem.

Bluez is userspace part of the bluetooth system. I don’t need bluetooth at all.

You can remove more like xserver-common, dbus, …

4.4 Change cmdline.txt to boot read-only

…and also skip filesystem check. Replace fsck.repair=yes with fsck.mode=skip. Append ro at the end. So your cmdline should end with :

fsck.mode=skip ro

4.5 Add “,ro” flag to both block devices in /etc/fstab

…to let the system know you want to mount them read-only:

proc              /proc           proc    defaults     0       0
/dev/mmcblk0p1    /boot           vfat    defaults,ro  0       2
/dev/mmcblk0p2    /               ext4    defaults,ro  0       1
tmpfs             /tmp            tmpfs   defaults     0       0

5. Watchdog

(I tested it on old sysv-based Raspian so information here may not be up to date)

It can be useful to set up a watchdog which can reboot your RPi in case something is unresponsive or eating CPU too much.

modprobe bcm2708_wdog #load BCM watchdog module
Add bcm2708_wdog into the /etc/modules so it gets loaded on boot.
apt-get install watchdog
EDIT: Newer Raspian uses bcm2835_wdt watchdog module instead.

Edit /etc/watchdog.conf:
Uncomment the line watchdog-device = /dev/watchdog
Uncomment the line with max-load-1

You can modify other parameters or find help online. Setting a minimum free RAM amount is a good idea. Before starting the watchdog, be prepared that you may have configured it wrongly and it will reboot immediately when you start it and may continuously reboot after each boot. So be prepared to modify your SD card on a different device if that happens.

Enable  the watchdog to start at boot and start it now:

insserv watchdog
/etc/init.d/watchdog start

During some modifications to your system (in read-write mode) later, you can consider disabling watchdog first. It rebooted my box once while I was doing some filesystem changes. Fortunately it booted fine for me, but it may not for you and may require manual, local fix.

In addition to the watchdog, you should set up reboot after a kernel panic. This is done by editing /etc/sysctl.conf. Add this line:

kernel.panic = 10

This will cause to wait 10 seconds after a kernel panic, then automatically safely reboot the box.

6. Add some cool utilities

5.1 syslog?

Newer systemd-based Raspian:

The situation is great with systemd-based raspian as journald is using RAM storage by default. You can additionally configure journald in /etc/systemd/journald.conf. Please follow the official documentation.

Older sysv-based Raspian:

It is helpful to receive syslog over the network. I think you can somehow enable sending busybox syslog over the network. I made my own script for this purpose, though. It reads output from ‘logread’ and sends it simply over the UDP to my server where it is saved to a logfile. Simple and helped a few times. Make sure to set up correct hostnames by editing /etc/hostname.

5.1 Cron?

Normal cron can’t be used unless you have an real external HW clock source. Because normally you can’t be sure that the clock got updated by NTP. If you can ensure it somehow, then fine, use cron. If not and using relative time is enough, you can make a fake cron using bash script, while loop and wait commands. Here is mine: (to be placed as /usr/local/fakecron.sh) https://paste.k3a.me/view/4515b0a4 . I use this startup script for it (to be placed to /etc/fakecron) https://paste.k3a.me/view/0a995efd.

7. Reboot!

Now it’s the best part. If you did everything correctly, it will boot just fine. If not, look at syslog (or journalctl -b) and try to find out why. You can fix the SD card in a different computer if the Pi doesn’t boot.

8. What to do next

Enjoy your reliable RPi. Good work! If you ever want to update the software, just remount the root filesystem as read-write temporarily:

mount -o remount,rw /

You may want to stop watchdog temporarily. Now run your apt-get etc stuff, modify what you need.. then mount read-only again:

mount -o remount,ro /


I don’t know why and if it is still true, but raspicam leaked memory for me, causing RPi to reboot after some time. I managed to improve it by disabling preview (-n) but still I set up RPi to reboot daily just to be sure……


And that should be it. Hopefully it helped. If it all works, back up your SD card using dd (google it https://www.google.cz/search?q=backup+using+dd).

If you have some tips, write them in comments. I can also update the article to include more info.

Please understand that I am often busy, so if you get stuck, please try google first. Consider asking at http://raspberrypi.stackexchange.com. If it won’t help, write a comment here and I will try to help you if I can.



  • http://blog.pi3g.com/2014/04/make-raspbian-system-read-only/
  • http://blog.gegg.us/2014/03/a-raspbian-read-only-root-fs-howto/
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Really, really nice advice!

I got to some similar results by the hard and time consuming way. So I really appreciate this excelkent compilation.

I have an important comment regarding the readonly configuration, that I am pursing by now: if i apply your suggestion, would i be able to write to GPIO pins (through wiring pi, symlinks or )

And what about mysql database updating, would it work or shall config it to be mounted in another partition or external usb sd unit.

Your insights will be much appreciated.



Thank you, master k3a.

Totally agree with corruption issues. That’s the goal that drove me to your excellent page.

Few considerations or questions:
You have experience on nginx, does it require to have some additional files to be mapped to tmpfs with symlinks or it keeps all logs to var/log etc.?

In a general way, how could I check which files are being written to for a specific app?Is there any file resources tracer? Or any tool to reveal files opened for rw (despite no writing is actually performed)?

Finally, about partitioning, obviously the partition to be written to might be worn out, but it shouldn’t affect the rootfs as long as they are “far away” in terms of the flash bytes that are written (i guess that for a single byte to be written to, the flash memory actually rewrites a complete chunk of them). Do you have any hint or rule for that?

If i have to mount an external sd connected to the usb port there might be some performance penalties. Some rough tests showed that it hardly reaches 3 MB/s



Hi ,

Thank you for writing this guide. Is there any idea on making the /etc/resolv.conf file writable? I want to make a clone of my setup, but when the system boots in read only, dhclient can’t update resolv.conf with the nameservers configuration retrieved from the dhcp server.

Obviously this will be a problem when the system is connected to a different network as the original one. Of course I can remount root as read write and restart network manually, but it will be cool if the system just works throughout different networks without manual intervention :)



Nevermind, installing package resolvconf solves this problem.


Hi, read everything here (nice work) and at http://blog.pi3g.com/2014/04/make-raspbian-system-read-only/ and if you have a min, i have a few questions:

1- On the other website, you mention a script you wrote to remount everything as RW temporarily but this was while using unionfs. On here you tell us to just use “mount -o remount,rw /” is that correct?

2- What are the other implications, beside cron? Can it mess with my scripts that uses date (to generate a unique filename) and sleep?

3- When you say “you can’t be sure that the clock got updated by NTP” do you mean in case there was an error like a network problem? If we rule that problem out shouldn’t cron work just fine with frequent ntp updates? or does the clock drift too much?

Thank you.

[…] How to make Rapberry Pi truly read-only, reliable and trouble-free […]


Hi k3b,

nice tutorial – thanks a lot for sharing it. Maybe some tip for you – busybox-syslogd has an option for setting a remote logserver: “-R HOST[:PORT]”. Check http://www.busybox.net/downloads/BusyBox.html for more information.

BTW: Do you ever tried something like overlayfs or aufs on “your solution”?



Hi, k3b!

Thanks a bunch for this, this is exactly what I need for my project.

A quick question for you, in step 4.6 you show how to add links for R/W files to tmp. Should I do this for /var/log as well?



[…] I found lot of interesting article with different methods and decided to start with this one from k3a, really thanks to […]


Hi k3a,
well, excellent article, really helped me a lot, I’ve published also on my blog truly based on your work, and added some interesting stuff like prompt indicating if read only or read write and save bash history at logout. You can take a look and grab back information if you want.
link is http://hallard.me/raspberry-pi-read-only/



As stated on https://www.kernel.org/doc/Documentation/filesystems/ext4.txt “ro” option doesn’t disable journaling. You should add “ro,noload” in fstab


Hi, I’ve tried your approach, but there still seem to be some changes made to the sd card.
I copied the sd card with dd and created a md5 checksum. The run the raspi again and checked the the md5 checksum again and they do not match!

Any ideas, why there are still changes made to the sd card?


Ok, thanks for your suggestions, i’ve tried vbindiff and it seems that only a few bytes at the very beginning are different.

Further research let me to the idea, that the superblock is modified when inserting the sd card to the PC.

sudo tune2fs -l
the superblock content can be displayed, and it shows, that the last mount time and mount count is modified everytime the sd card is mounted on the PC.

I will try to disable automount and retry mounting the sd card read only on the pc to.

I’ll post the results as soon as available.


really helpful article!

one question about : 2. Remote shell
how many connections a server can handle?
is vpn a better idea than this method?


Very cool. What is the version of your pi ? Have you tried for RaspPi2 with version 8?


seems a reasonable choice, got another option for some situation, really thanks!


ro Mount filesystem read only. Note that ext4 will
replay the journal (and thus write to the
partition) even when mounted “read only”. The
mount options “ro,noload” can be used to prevent
writes to the filesystem.


Hi k3a,

Thank you for writing this detailed tutorial. It’s really helpful and I successfully get the file system read-only. But I have a few questions that may apply only to my setup:

I partitioned the SD card to have 4 partitions in total:
1. boot – read-only
2. / – read-only
3. /opt – read-write
4. /var/log – read-write

Q1. I can’t use wifi dongles to connect to Internet, but Ethernet works fine. Any way we can get WiFi working?
Details: after mounting the file systems read-only and reboot, the /etc/network/interfaces file cannot be created because it’s under /etc/network/ directory and it is read-only. I have a static wpa_supplicant.conf file with all the APs in /opt/ and created a symlink for /etc/wpa_supplicant/wpa_supplicant.conf. WiFi works fine before I mounted file systems read-only so my WiFi dongle is working fine.

Q2. I didn’t remove fake-hwclock, and I have a script written to synchronize the time with our server, so I assume in this case cron will work fine?


John Beardmore

I tried the above and the system boots with the file system ro.

So far so good, but the directoried that were linked to /tmp don’t seem to be, though I don’t recall seeing any error reports when I did the ln -s commands.

By the way, is there any reason why apache won’t work on a system with /root ro? Similarly, could X11 and remote desktop access work? Both did, neither do now.

Cheers, J/.


Thanks for your reply! I got it working. There are two things that were incorrectly set.
1. /tmp was mounted under /, so symlinks to /tmp didn’t work
2. I also have to symlink /etc/resolv.conf to /tmp/resolv.conf, otherwise DNS won’t work.
Now everything is working and hopefully the SD card will be much more reliable than before!



I am running OSMC on Pi 2 as an HTPC. A DS1307 real time clock is connected to the Pi, as the device is usually not connected to the network.
I want to configure the device for direct a power off, just like a TV (without a proper shut down).
I have a few questions on this:
1. If make it a read only system, will I be able to directly pull the power plug without damaging the file system.
2. In case it is a read only system, will it not save any settings that I change while running KODI (Language settings, WiFi password etc).
3. I followed the steps mentioned by you on my OSMC in order to make it read-only. And since I am not good at Pi software, I followed the steps to the letter. But it did not work. The OSMC did not boot after making the changes.

Could you please guide me. I don’t want to add any hardware/UPS etc to shut it down safely.


Thanks a lot for the help.
I’ll do it again and will follow the step three mentioned in your reply.
In case of failure, I think I’ll be able to provide the logs as the whole boot sequence is displayed on screen.
And thanks again for the response. If I succeed this time, your article would save me a lot of effort and money that I was going to spend on additional, space consuming hardware.



thanks for your post, I follow it and works fine but after final reboot I can’t no more access via ssh???

Any trick to find out what’s wrong with my PI?


Hi k3a

thanks for this really nice story.
It works for me generally. However I made a strange observation.
After bootup the /tmp directory has restricted access rights and some of my startup applications do not run because they want to write a log which I ln-ked to /tmp

drwxr-xr-x 11 root root 360 Dec 13 19:53 tmp

Even I specify mode=777 in fstab, this does not help.

tmpfs /tmp tmpfs rw,mode=777 0 0

I am running the newest Raspbian Jessie. Maybe this issue has something to do with systemd which processes fstab ?


Here you are:
root@pibplus:/home/pi# mount
/dev/mmcblk0p2 on / type ext4 (ro,relatime,data=ordered)
devtmpfs on /dev type devtmpfs (rw,relatime,size=242612k,nr_inodes=60653,mode=755)
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
proc on /proc type proc (rw,relatime)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
tmpfs on /run type tmpfs (rw,nosuid,nodev,mode=755)
tmpfs on /run/lock type tmpfs (rw,nosuid,nodev,noexec,relatime,size=5120k)
tmpfs on /sys/fs/cgroup type tmpfs (ro,nosuid,nodev,noexec,mode=755)
cgroup on /sys/fs/cgroup/systemd type cgroup (rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/lib/systemd/systemd-cgroups-agent,name=systemd)
cgroup on /sys/fs/cgroup/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,cpuset)
cgroup on /sys/fs/cgroup/cpu,cpuacct type cgroup (rw,nosuid,nodev,noexec,relatime,cpu,cpuacct)
cgroup on /sys/fs/cgroup/blkio type cgroup (rw,nosuid,nodev,noexec,relatime,blkio)
cgroup on /sys/fs/cgroup/devices type cgroup (rw,nosuid,nodev,noexec,relatime,devices)
cgroup on /sys/fs/cgroup/freezer type cgroup (rw,nosuid,nodev,noexec,relatime,freezer)
cgroup on /sys/fs/cgroup/net_cls type cgroup (rw,nosuid,nodev,noexec,relatime,net_cls)
systemd-1 on /proc/sys/fs/binfmt_misc type autofs (rw,relatime,fd=22,pgrp=1,timeout=300,minproto=5,maxproto=5,direct)
debugfs on /sys/kernel/debug type debugfs (rw,relatime)
mqueue on /dev/mqueue type mqueue (rw,relatime)
configfs on /sys/kernel/config type configfs (rw,relatime)
tmpfs on /tmp type tmpfs (rw,relatime,mode=777)
/dev/mmcblk0p1 on /boot type vfat (ro,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=ascii,shortname=mixed,errors=remount-ro)
root@pibplus:/home/pi# stat /tmp
File: ‘/tmp’
Size: 320 Blocks: 0 IO Block: 4096 directory
Device: 1dh/29d Inode: 5375 Links: 10
Access: (0755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 1970-01-01 01:00:07.670000000 +0100
Modify: 1970-01-01 01:01:41.700000000 +0100
Change: 1970-01-01 01:01:41.700000000 +0100
Birth: –


pi@pibplus ~ $ echo test > /tmp/test
-bash: /tmp/test: Keine Berechtigung

Sorry, thats German, but it means as you would expect: no permission (to write)
I can change the permissions manually of course or in /rc.local with chmod 777 /tmp and then all is fine.
But I would need the permissions right DURING startup, not at the end.
I think the systemd doesn’t understand the mode=777


ok, thanks, will do the same


Oh, the file on my raspi looks the same. I also tried to edit the Options as 777 and deleted the other parameter but no change, still write permissions missing.


Yes, rebooted all the time of course.
This is my output here.
Its not looking as it should be.

root@pibplus:/home/pi# systemctl status tmp.mount
â tmp.mount – /tmp
Loaded: loaded (/etc/fstab; enabled)
Active: active (mounted) since Mon 2015-12-14 20:24:19 CET; 1min 55s ago
Where: /tmp
What: tmpfs
Docs: man:fstab(5)
Process: 143 ExecMount=/bin/mount -n tmpfs /tmp -t tmpfs -o rw,mode=1777 (code=exited, status=0/SUCCESS)

Dec 14 20:24:19 pibplus systemd[1]: Mounted /tmp.
root@pibplus:/home/pi# ls -l /
drwxr-xr-x 10 root root 340 Dec 14 20:25 tmp

[…] How to make RaspberryPi truly read-only, reliable and trouble-free […]


Mostly worked for me, but am getting a couple of errors during boot up. The one that seems most serious is, I think, related to dhcpcd:

pi@ospi:/etc/network/run $ systemctl status dhcpd.service
Failed to get D-Bus connection: No such file or directory
pi@ospi:/etc/network/run $ sudo systemctl status dhcpd.service
● dhcpd.service
Loaded: not-found (Reason: No such file or directory)
Active: inactive (dead)

One significant piece of fallout is that DNS lookup does not work. Where should I look to try to run this down. Please don’t assume that I’ve checked the places that would be obvious.



Nevermind. I think I’ve fixed it. It was really a systemd problem requiring adjustment of the associated service file so that it wrote the PID file to /tmp.




I found this to be very helpful, and I still use it as reference. I do have a question, do you think it would be possible to extend this so that the file system is contained in a loopback file on the FAT formatted boot partition? Where I work I’m receiving resistance to additional Raspberry Pis because the Windows centric technicians don’t understand how the file system is ‘hidden’ in the ext3/4 partition. Using a loopback file might allow all files necessary to boot a Pi to be on a standard FAT formatted SD card where the user simply needs to copy the necessary files, even on a Windows box.



I use my Rasberry as a NAS server. Is it recommend to set read-only mode then? I tried do it but sth came wrong and my computers don’t see rasberry now. I set everything the same like in that tutorial https://hallard.me/raspberry-pi-read-only/ but there are some differences between that and yours. Now I don’t know if I should reset everything and stay in read-write mode or try to do set read-only once again with your tips..


Thank you for this, it was very helpful.
Unfortunately, I was using it to protect an installation that was running video-looper on startup and now video-looper will no longer autorun. do you know what I might have removed or changed that would interfere, and is it possible to use this program with a read only card?


Thanks for this. It really gives the stability to micro SD card that I need.

I have one question that may not be really about this topic, but in some way it is. I developed a Qt application which is basically a dummy application. It receives messages and images over UDP sockets, and shows them on the screen. The problem I have is that when I am in read-only mode application just aborts after about half a second or so. When it is run in read-write mode it works great.

After removing chunks of code and testing it in read-only mode I found out that if application don’t process received messages, which i really have to since that’s the only functionality application has, it doesn’t get aborted. I am not that good with Linux to be honest, but what seems logical to me is that when I read that data in application it needs to be stored somewhere, and that somewhere is in read-only part of memory.

Does what I wrote make any sense? If yes which parts of file system need to be mounted as tmpfs to fix it? If not what is actually happening and is it possible to fix it somehow?

By the way I am using Raspbian Jessie Lite if that means something to you.

Thanks in advance


Hi. Can you please post how you fixed it – I have the same problem with latest jessie/systems in ro ? Thanks. Tomas


Just a great helb to get started with ro :-)

Is this kompatible with apache?

I tried to build a RPI – SVN-Server with:
sd-card = ro
2xUSB-stick as btrfs raid1 mounted to /media/usb_raid1

I folled jeremy’s intruction to install svn + apache for svn webaccess:

BUT: unfortunately apache doesn’t want to start … because of missing dbus?
Is there a way to use application that usually expact dbus?


Would love your thoughts, please comment.x
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