How to have RPi-Monitor report available/used memory on 3.4 kernels

Hi. When you install RPi monitor on a board using legacy 3.4 kernel (in my case, Orange Pi Plus2e), you can notice an error message in the "Memory" section of the web interface, as well as a very weird big number of used memory.

That is caused because it tries to read some value from /proc/meminfo (named "MemAvailable") that wasn't implemented in that version of the kernel (I think it was implemented in 3.14, if I remember well).

So I have made a custom version of the memory module, which gets the value for used and available memory using the same algorythm as HTOP, which has been many years around being very useful. I am attaching the file "memory_legacy.conf". In order to use it:

1. Copy it to /etc/rpimonitor/template/
2. Edit /etc/rpimonitor/data:

   Change:
   include=/etc/rpimonitor/template/memory.conf
   
   for:
   include=/etc/rpimonitor/template/memory_legacy.conf

    

Maybe the devs could include it in the default installation, if they see fit.

memory_legacy.conf