pi-ramdisk

Alongside a project using a Raspberry PI, I became quite concerned as several SD cards had been ruined by various PI projects in the past. Given the Raspberry Pi 4 has 8GB of RAM (well, at least that specific model) I figured it was time to figure out how to make this work. I am still a linux noob, so I decided to put my learnings into a readme to help future me's in the making.

Background:

Some people complain that the Raspberry Pi ruins SD Cards. Principle reason for this is that there is no obvious off button for the Pi. This leads people to assume that the only way is to pull the power cable. Repeated episodes of this over a long time eventually causes irrecoverable corruption of SD Card. I don't have conclusive knowledge either way - but people seem to get animated about this - Check out this link: https://www.raspberrypi.org/forums/viewtopic.php?t=202381

Major points - how I broke it:

• configurations for this are in /etc/fstab
• if you do this, anything you put there will be lost on boot. (this was suitable for a particular project for me, and worthwhile doing)
• if you mess this up, you have to rescue your system in "single user mode"
  • copying and pasting text from OneNote into /etc/fstab whilst using Putty will put invisible bad charaters into your file and it wont boot
  • i put text into notepad and copied out again, and then run 'dos2unix against it - this tool is accessible in the distro (if you sudo apt install it first)

Single user mode gotcha:

• if you haven't put a password on your root account (unlikely - nothing I've seen so far actually asks) you won't be able to rescue it using linux boot methods
  • I found a link that took me through holding a key at a certain moment, which took forever
• if you are using a raspberry pi, thankfully they have a text file which you can edit boot properties with and still fix it
  • Instructions for this are at: https://linux.tips/tutorials/how-to-boot-raspberry-pi-into-single-user-mode

New Lines in my /etc/fstab file:

tmpfs                 /tmp            tmpfs   defaults,noatime,nosuid,size=100m   0       0
tmpfs                 /var/tmp        tmpfs   defaults,noatime,nosuid,nodev,noexec,size=100m,mode=0755    0       0
tmpfs                 /var/log        tmpfs   defaults,noatime,nosuid,mode=0755,size=100m,mode=0755      0       0
tmpfs                 /var/run        tmpfs   defaults,noatime,nosuid,mode=0755,size=100m,mode=0755       0       0

Lines I wan't sure about:

tmpfs    /var/spool/mqueue    tmpfs    defaults,noatime,nosuid,mode=0700,gid=12,size=50m    0 0

a swapfile is not a swap partition, no line here use dphys-swapfile swap[on|off] for that

Final notes:

• Other paths could go there, and such ram disk sizes could also change. Some have a mandatory minimum.
• RAM is not hard allocated at boot time - it is only consumed as it is used.