low write mode causing problems

I’ve followed the guide to activate the low write mode in emoncms step by step but now the webpage is not available anymore and I’m getting a http error 500

I’ve double checked the steps and found that the feedwriter service is not running …

I don’t know if this is causing the issue and how to solve this? Can someone please help … I’m not the RPi pro … sorry!


Hi, welcome.

How did you install Emoncms in the first place?

Those guides are out of date so that might be the issue.

Out of date? Really? Is there no low write mode possible anymore?
I’m using Version 9.9.8 as I don’t like the new GUI - so I will stick with this version! Maybe there is an low-write mode still possible / needed?

BTW - I would appreciate an update instead of archive!

In your last screenshot above it highlights a syntax error in your settings.php file, it looks like it’s having trouble reading it.

The problem is that the new version does not just include a new GUI, but lots of backend fixes. It is really difficult to support older versions. It is a bit like asking Microsoft to support XP because you do not like Win 10 interface (or old MacOS or old Ubuntu versions depending on your view).

For instance, there were some issues with the python scripts that support low write. These have been fixed but very difficult to back port. If you pull in the new script, it may well now be incompatible with v9.9.8.

Low write is necessary else the SDCard will wear out quite quickly (assuming it is on an SDCard based system). It is still possible but the implementation is not exactly the same.

Maybe so, but with limited effort available that is unlikely to happen.

A lot of effort has gone into the new scripts to help avoid the need for these different guides that tended to get out of sync.

Well Microsoft don’t support XP now, but they did for 12 years, alongside various other OS. Ubuntu is currently supporting two releases. Most vendors support more than one. I believe Apple support three versions of MacOS at one time. So I don’t think that was a very good point!

FWIW, I’m running ‘low-write 9.9.8’ quite happily. /var/log uses 8.7 MB out of 42 MB. /run/log/journal uses 49 MB out of 440 MB. The pi has been up for 86 days.

It seems to me that keeping images of releases for long enough to decide whether they work well, perhaps with some subsequent patches installed, and then freezing them but keeping them available, is very doable without much effort.

@djh: I had exactly the same thought that XP is definalty NOT a good example :slight_smile: You made may day!

Can you tell me how to get the low wirte mode activated with 9.9.8? I want to protect my SD-card and your input would be highly appreciated!


I’m sure you will be able to help @Hecot out then. I’m reasonably sure that you are not running ‘vanilla’ 9.9.8 and have had to do other things such as modify logrotate to keep it happy.

The image is not one single thing (which is why it is referenced by date rather than Emoncms Version) and equally, Emoncms V9.9.8 is just one part of the overall system which is why, what you suggest, simply will not work considering a lot of the help offered here is ‘community’ rather than paid for.


You’d think so, wouldn’t you? I am running something that describes itself at the bottom of the pages ‘low-write 9.9.8’ and I’m pretty certain I didn’t put that there. I certainly had to do some things to get it to run properly - and that’s why I still run it, because I expect I’d have to do some other bunch of things to get any upgrade to run properly as well, and what I want is just a stable logging system, not a toy to play with. But I’m afraid I don’t remember exactly what I did, so I’m not much help to Hecot.

The one thing I do remember is that I had to change the logging levels to reduce the quantity of ‘garbage’ spewed out by MQTT (?) But for any other changes it will be necessary to trawl the archives to find the posts where you or Trystan or Robert or Paul or … I’m sure there were others … told me what needed changing to make it work. :slight_smile:

The image definitely is just one thing - it’s an SD card bought from the shop. The changes do complicate things a bit, I agree, but AIUI git is quite capable of tracking multiple changes and it’s then just a matter of noticing which versions actually work. If the original image I started with is identified internally by some kind of UID and if it is still available online, then we could probably work out pretty much how mine differs from it with diff or similar (git?).

Oh, FWIW the last thing in /var/log/emoncms.log is:
2019-07-27 23:07:03.614|WARN|phpmqtt_input.php|Connecting to MQTT server: Connection Accepted.: code: 0

Other details are as follows:

Server Information
emonhub Active Running
mqtt_input Active Running
feedwriter Active Running - sleep 60s
service-runner Active Running
emonPiLCD Active Exited
redis-server Active Running
mosquitto Active Running
Emoncms Version low-write 9.9.8
Modules Administration : App v1.2.0 : Backup v1.1.5 : EmonHub Config v1.0.0 : Dashboard v1.3.1 : Device v1.2.0 : EventProcesses : Feed : Graph v1.2.1 : Input : Postprocess v1.0.0 : CoreProcess : Schedule : Network Setup v1.0.0 : sync : Time : User : Visualisation : WiFi v1.3.0
Git URL: GitHub - emoncms/emoncms: Web-app for processing, logging and visualising energy, temperature and other environmental data : Branch: * stable : Describe: 9.9.8-4-gd0db7a57
Server OS Linux 4.14.71-v7+
Host emonpi : emonpi : (
Date 2019-10-22 18:57:13 UTC
Uptime 18:57:13 up 86 days, 19:42, 1 user, load average: 0.19, 0.11, 0.09
HTTP Server Apache/2.4.25 (Raspbian) HTTP/1.1 CGI/1.1 80
MySQL Version 5.5.5-10.1.23-MariaDB-9+deb9u1
Host (
Date 2019-10-22 18:57:12 (UTC 00:00‌​)
Stats Uptime: 7501828 Threads: 2 Questions: 459609 Slow queries: 0 Opens: 29 Flush tables: 1 Open tables: 19 Queries per second avg: 0.061
Redis Version 3.2.6
Host localhost:6379 (
Uptime 86 days
MQTT Server Version Mosquitto 1.4.10
Host localhost:1883 (
Pi Model Raspberry Pi 3 Model B+ Rev 1.3 - 1 GB (Sony UK)
SoC Broadcom BCM2835
Serial num. 6FD53142
Temperature CPU: 57.46°C - GPU: 58.0’C
Release emonSD-30Oct18
Memory RAM Used: 20.69% Total: 976.74 MB Used: 202.12 MB Free: 774.62 MB
Swap Used: 0.00% Total: 100 MB Used: 0 B Free: 100 MB
Disk Mount Stats
/ Used: 45.79% Total: 3.81 GB Used: 1.75 GB Free: 1.89 GB
/boot Used: 51.69% Total: 42.52 MB Used: 21.98 MB Free: 20.54 MB
/home/pi/data Used: 2.97% Total: 10.32 GB Used: 314 MB Free: 9.48 GB
PHP Version 7.0.30-0+deb9u1 (Zend Version 3.0.0)
Modules apache2handler : calendar v7.0.30-0+deb9u1 : Core v7.0.30-0+deb9u1 : ctype v7.0.30-0+deb9u1 : curl v7.0.30-0+deb9u1 : date v7.0.30-0+deb9u1 : dom v20031129 : exif v7.0.30-0+deb9u1 : fileinfo v1.0.5 : filter v7.0.30-0+deb9u1 : ftp v7.0.30-0+deb9u1 : gd v7.0.30-0+deb9u1 : gettext v7.0.30-0+deb9u1 : hash v1.0 : iconv v7.0.30-0+deb9u1 : igbinary v2.0.1 : json v1.4.0 : libxml v7.0.30-0+deb9u1 : mbstring v7.0.30-0+deb9u1 : mcrypt v7.0.30-0+deb9u1 : mosquitto v0.4.0 : mysqli v7.0.30-0+deb9u1 : mysqlnd vmysqlnd 5.0.12-dev - 20150407 - $Id: b5c5906d452ec590732a93b051f3827e02749b83 $ : openssl v7.0.30-0+deb9u1 : pcre v7.0.30-0+deb9u1 : PDO v7.0.30-0+deb9u1 : pdo_mysql v7.0.30-0+deb9u1 : Phar v2.0.2 : posix v7.0.30-0+deb9u1 : readline v7.0.30-0+deb9u1 : redis v4.1.1 : Reflection v7.0.30-0+deb9u1 : session v7.0.30-0+deb9u1 : shmop v7.0.30-0+deb9u1 : SimpleXML v7.0.30-0+deb9u1 : sockets v7.0.30-0+deb9u1 : SPL v7.0.30-0+deb9u1 : standard v7.0.30-0+deb9u1 : sysvmsg v7.0.30-0+deb9u1 : sysvsem v7.0.30-0+deb9u1 : sysvshm v7.0.30-0+deb9u1 : tokenizer v7.0.30-0+deb9u1 : wddx v7.0.30-0+deb9u1 : xml v7.0.30-0+deb9u1 : xmlreader v7.0.30-0+deb9u1 : xmlwriter v7.0.30-0+deb9u1 : xsl v7.0.30-0+deb9u1 : Zend OPcache v7.0.30-0+deb9u1 : zlib v7.0.30-0+deb9u1
Client Information
HTTP Browser Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Firefox/60.0
Screen Resolution 1920 x 1080
Window Size 1170 x 780

As you can see, Emoncms is just one part of the system - bit like Android plus apps.

Exactly my point. Those issues are now fixed in the latest release (and to some extent, finding those solutions and incorporating them make each release better) so unless everyone does those fixes individually they will each have the same issues.

You clearly do not understand it is multiple repositories. If you think it is possible you are welcome to try.

Anyway, I’m done. As far as I’m concerned 9.9.8 is not supported by me now there is a new stable release - others may have a different view.

Trystan posted this yesterday but it seems to have been missed???

That error actually appears three times in the second screenshot of output in the first post.
@Hecot have you checked your settings.php file for syntax errors?

Thanks for all your posts! What I learned is that a solution is not just as easy as I thought.

I already did a complete roll-back to an older image that was working well and I’m sure I will stick with what I have for a longer time (maybe years) and not do any update of emoncms as I don’t know what new problems will arrise!

@djh I fully support your quote! A colleague just said “home automation is what model railways was in the 80 ties - a nice toy for boys at heart!” :smiley:

Meanwhile I’ve purchased a SSD and will run emoncms from there - problem solved!

Thanks again and all the best!