{"id":218,"date":"2015-04-19T22:48:49","date_gmt":"2015-04-19T21:48:49","guid":{"rendered":"https:\/\/blog.lemongrass.org.uk\/lemongrass\/?p=218"},"modified":"2015-04-21T01:16:55","modified_gmt":"2015-04-21T00:16:55","slug":"setting-up-raspberry-pi-for-emoncms-with-data-on-an-nfs-mount","status":"publish","type":"post","link":"https:\/\/blog.lemongrass.org.uk\/lemongrass\/setting-up-raspberry-pi-for-emoncms-with-data-on-an-nfs-mount\/","title":{"rendered":"Setting up Raspberry Pi for EmonCMS with data on an NFS mount"},"content":{"rendered":"

The instructions\u00a0 for installing Emoncms on the Raspberry Pi <\/a>are at available through the OpenEnergyMonitor<\/a> site.\u00a0 However I had to take some additional steps.\u00a0 This page lists what I did, drawing heavily from those instructions with thanks.<\/p>\n

I used a Raspberry Pi 2 model B.\u00a0 This has Ethernet which I needed to connect to the network, though you could use a Wifi dongle.\u00a0 Before you can use the Pi, you have to install its operating system on a micro-SD card\u2013I used an 8Gbyte one.\u00a0 To receive wireless data from emonTx and emonTh modules, you need an expansion card such as the RFM69Pi<\/a>.<\/p>\n

Install Raspbian<\/h3>\n

Using Windows, fetch the Raspbian installation image<\/a>.\u00a0 Extract the zip file to obtain the single image file, in my case called 2015-02-16-raspbian-wheezy.img.\u00a0 Write this image to the micro-SD card using Win32DiskImager<\/a>.\u00a0 Insert the micro-SD card into the Raspberry Pi (it goes in upside down) and power up. Watch in amazement as the boot images whizz by on the HDMI-connected monitor.\u00a0 The initial screens allow you to set the password for the “pi” user, and if you are not based in the UK, you can change the Internationalisation options.<\/p>\n

The EmonCMS installation instructions suggest making an additional data partition on the SD card.\u00a0 I preferred not to do this for two reasons: the data is precious and the SD card has limited life, even with the write buffering.\u00a0 Instead, I plan to mount a shared folder from my Synology NAS drive to hold the data.\u00a0 I cover this in a separate post, as it is tricky.\u00a0 However, following the instructions caused the root filesystem to overflow during the installation of pre-requisite software, so I recommend expanding the filesystem to the full size of the SD card.\u00a0 There’s an option to do this in the initial configuration screens.\u00a0 If you’ve already exited, type “sudo raspi-config” to re-invoke the configuration screeen.<\/p>\n

Disable Serial Port login<\/h3>\n

By default, Raspbian Wheezy is configured to support login on the serial port.\u00a0 This would conflict with the use of that port for radio communications, so we need to disable logins on the serial port.\u00a0 Edit the configuration files as follows:<\/p>\n

sudo nano \/etc\/inittab<\/pre>\n
At the bottom of the file comment out the last line, by adding a \u2018# \u2019 at the beginning:<\/p>\n
# T0:23:respawn:\/sbin\/getty -L ttyAMA0 115200 vt100<\/pre>\n
[Ctrl+X] then [y] then [Enter] to save and exit.\u00a0 Next, edit the boot command line:<\/p>\n
sudo nano \/boot\/cmdline.txt<\/pre>\n
Raspbian has been updated since the Emoncms instructions were written, and the line to change is now a little different.\u00a0 Remove “console=ttyAMA0,115200” from the line, so that it reads<\/p>\n
dwc_otg.lpm_enable=0 console=tty1 root=\/dev\/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait<\/pre>\n
Change the filesystem to be mounted read-only<\/h3>\n
To reduce wear on the SD card, the filesystem can be mounted read-only, except when software updates are necessary.\u00a0 The data will be stored on an external NAS drive. Before switching to read-only mode, we need to create commands to switch between read-only and read-write modes, and create a mount-point for the data partition. Do this while logged in as “pi”.<\/p>\n
mkdir \/home\/pi\/data<\/pre>\n
Turn on the TMPFS filesystem:<\/p>\n
sudo cp \/etc\/default\/tmpfs \/etc\/default\/tmpfs.orig\r\nsudo nano \/etc\/default\/tmpfs<\/pre>\n
Find the line that says<\/p>\n
#RAMTMP=no<\/pre>\n
Change it by removing the “# ” at the beginning of the line and changing “no” to “yes”:<\/p>\n
RAMTMP=yes<\/pre>\n
Use [Ctrl+X] then [y] then [Enter] to save and exit.<\/p>\n
Next, replace the filesystem mount point table:<\/p>\n
sudo mv \/etc\/fstab \/etc\/fstab.orig\r\nsudo sh -c "echo 'tmpfs\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \/tmp\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 tmpfs\u00a0\u00a0 nodev,nosuid,size=30M,mode=1777\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 0\u00a0\u00a0\u00a0 0' >> \/etc\/fstab"\r\nsudo sh -c "echo 'tmpfs\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \/var\/log\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 tmpfs\u00a0\u00a0 nodev,nosuid,size=30M,mode=1777\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 0\u00a0\u00a0\u00a0 0' >> \/etc\/fstab"\r\nsudo sh -c "echo 'proc\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \/proc\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 proc\u00a0\u00a0\u00a0 defaults\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 0\u00a0\u00a0\u00a0 0' >> \/etc\/fstab"\r\nsudo sh -c "echo '\/dev\/mmcblk0p1\u00a0 \/boot\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 vfat\u00a0\u00a0\u00a0 defaults\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 0\u00a0\u00a0\u00a0 2' >> \/etc\/fstab"\r\nsudo sh -c "echo '\/dev\/mmcblk0p2\u00a0 \/\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 ext4\u00a0\u00a0\u00a0 defaults,ro,noatime,errors=remount-ro 0\u00a0\u00a0\u00a0 1' >> \/etc\/fstab"\r\nsudo sh -c "echo '192.168.10.102:\/volume1\/emonpi2\u00a0 \/home\/pi\/data\u00a0\u00a0 nfs \u00a0\u00a0 user=pi \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 0\u00a0\u00a0\u00a0 0' >> \/etc\/fstab"\r\nsudo sh -c "echo ' ' >> \/etc\/fstab"\r\nsudo mv \/etc\/mtab \/etc\/mtab.orig\r\nsudo ln -s \/proc\/self\/mounts \/etc\/mtab<\/pre>\n
Note: The line referring to \/home\/pi\/data will need to be changed to reflect your NAS drive’s IP address (or DNS name) and shared folder path.\u00a0 See my separate post for instructions on making this work with Synology DiskStation DSM 5.1.<\/p>\n
Create the commands to switch between read-only and read-write mode:<\/p>\n
sudo nano \/usr\/bin\/rpi-rw<\/pre>\n
In the empty file which loads, enter the following:<\/p>\n
#!\/bin\/sh\r\nsudo mount -o remount,rw \/dev\/mmcblk0p2\u00a0 \/\r\necho "Filesystem is unlocked - Write access enabled"\r\necho "Type 'rpi-ro' to lock"<\/pre>\n
[Ctrl+X] then [y] then [Enter] to save and exit, and then type the following to make the command executable:<\/p>\n
sudo chmod +x\u00a0 \/usr\/bin\/rpi-rw<\/pre>\n
Similarly, create the opposite script:<\/p>\n
sudo nano \/usr\/bin\/rpi-ro<\/pre>\n
In the empty file which loads, enter the following:<\/p>\n
#!\/bin\/sh\r\nsudo mount -o remount,ro \/dev\/mmcblk0p2\u00a0 \/\r\necho "Filesystem is locked - Write access disabled"\r\necho "Type 'rpi-rw' to unlock"<\/pre>\n
[Ctrl+X] then [y] then [Enter] to save and exit, and then type the following to make the command executable:<\/p>\n
sudo chmod +x\u00a0 \/usr\/bin\/rpi-ro<\/pre>\n
Reboot to bring the changes into effect:<\/p>\n
sudo shutdown -r now<\/pre>\n
Log in again and change the permissions on the data directories. This may bring up error messages when using the Synology NAS.<\/p>\n
sudo chmod -R a+w data\r\nsudo chown -R pi data\r\nsudo chgrp -R pi data<\/pre>\n
Continue to follow the instructions from “Installing Dependencies” in the instructions in installing Emoncms on the Raspberry Pi.<\/a>\u00a0 However, it turns out it is not really feasible to run MySQL with its data directory NFS mounted from Synology DSM.\u00a0 This is due to a number of factors:<\/p>\n