Posted on Friday 16th March 2018
This started to become a problem for me when was running a monitoring script which wrote to a file every 10 mins. After seeing SD Card failures I opted to move the OS to a USB and run off the usb just like you can on a full computer as detailed in https://www.chris-shaw.com/blog/install-ubuntu-16.04-persistently-on-a-usb-drive
The following instructions are written with the intent of being carried out on windows, but the instructions are similar for all platforms but you may need to use different tools, for instance if I was to do this on Ubuntu I would use the Disks application for the formatting of the drives and UNetBootin to write to the USB and SD card.
Plug the USB drive into the PC and format to fat32. There are several ways to do this and you can find some of these in https://www.maketecheasier.com/format-usb-drives-windows-10/
The option I went for was to Open up File Explorer, right click the USB drive an Choose the Format option.
Repeat for the SD Card.
Using Rufus pictured below, select the USB drive and load the img file for raspbian. When you click start it will begin writing the image to the usb.
Using File Manager, drag the entire contents of the USB to the SD Card.
The trick to this method is during the boot process we need to change where the files for the OS are located. On the SD card will be a file called cmdline.txt which tells the pi where the files are. In this file we need to change the following line
At this point we need can insert the sd card and the usb drive into the raspberry pi and boot up. It works but the storage is limited and not using the full capacity of the USB drive.
Following are the steps to expand the filesystem on the USB Drive
sudo fdisk /dev/sda
Press p to see the partitions, there should be two here.
Press d then the number of the partition, usually 2.
sudo resize2fs /dev/sda2
At this point the USB drive will have access to its full capacity.