REDUCING SD CARD WRITES USING TMPFS
I introduced a feature on my mains frequency website that calculates the average mains frequency over a 24-hour period. It maintains a file of the last 86400 readings and recalculates the average every second. It writes this file to the SD card and I was concerned about the impact this may have on the card's lifetime. I changed the way this feature worked so that the file was on placed on a tmpfs filesystem, essentially only ever in volatile memory, in order to spare the SD card. A tmpfs filesystem can be set up easily following the steps below.
Set up a new directory:
sudo mkdir /virtual
Edit /etc/fstab and add a record for /virtual, highlighted below. The 1M is the upper limit for the total size after which swap may occur and the noatime disables file access times from being updated.
|# a swapfile is not a swap partition, no line here
|# use dphys-swapfile swap[on|off] for that
Mount the new filesystem.
sudo mount -av
And you're ready to go!