new emonpi build using emonSD-17Jun2015.img mysqld fails to start



i've been using openemon for a while now, using an emonpi, and 2 emontx v2 nodes that forward to my own cms server.

took a while to get it all working but it's great and i love it!

i'm setting up a new similar set for a friend, but when using the new emonSD-17Jun2015.img image. on first, and any subsiquent boot the mysqld service won't start. i can't start it by hand either.

i have tried a number of SD cards, both 4G and larger, but all with the same effect. It's really odd!

when i use the emonpi-28May2015.img older image it still fails

having searched the forums, no one else mentions this, which makes me thing it's something specific to my setup.

but its the virgin image that fails...

i have also tried running the firmware updater, which runs fine. But the mysqld still fails to start post reboot.

running on a pi b 256mb  - tried it another model and i fails

but runs on a 512mb ok

i had nothing like this problem last time, just install and go

there is nothing in the docs about this limitation is there?


many thanks,




pb66's picture

Re: new emonpi build using emonSD-17Jun2015.img mysqld fails to start

I think you may be running out of RAM, the fact it runs on 512 but not 256 sort of confirms this theory, The "emonPi SDcard" images will require a bit more than the previous images as it is also running a mqtt broker and various other services for the wifi monitoring, mqtt in emoncms, the logging and configuration pages etc.

The pre emonPi images are probably more likely to run on a 256mB Pi but to be honest I think even the older image needs the 512mB for some headroom, it is running SQL, redis and apache2 servers without any memory caching (read-only mode) all the logs are written to RAM and emonhub runs an in memory buffer which is normally very minimal but any network issues will cause emonHub to stack data up in RAM and could choke the Pi. From memory I think mySQL 5.5 has 128mB in-memory cache and then there is redis in-memory buffer too.

IMO a 256mb Pi should only run as a forwarder, the 'rock solid gateway' style using emonHub only (no emoncms etc), 512mb min for a full "pre-emon-pi" emonhub + emoncms and the latest "emonPi" images should ideally only be used on a 1gb Pi unless emoncms is disabled or some restraint is applied.

The previous image you tried is still the emonPi type, the pre-emonPi images are still supported although a little harder to track down, the OLD: Raspberry Pi 2 pre-built SD card image (emonSD-13-03-15.img) BETA thread has links


euridium's picture

Re: new emonpi build using emonSD-17Jun2015.img mysqld fails to start

hello Paul,

thanks for the information and confirmation.

is there a recipe / method to take the "emonsd" image and make it into that rock solid gateway with emon hub?

i know that i could just stop the mysqld service and apache service, not sure what other dependencies rely on this though.

i assume that the emon hub config is a text file somewhere, and that it isn't dependent of apache or anything else?

Thanks again,





pb66's picture

Re: new emonpi build using emonSD-17Jun2015.img mysqld fails to start

The links to the guides are broken due to the github branch being renamed

"Using the pre-built image:"

should link to

"Technical overview and image build guide:"

should link to

most of the info you need will be on 

attached is a changelog for the pre emonPi image and it looks like the last versions did not have emoncms enabled so should "just work out of the box" 


Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.