SPECIAL NOTE ABOUT THE PI - Do not "hotplug" USB devices, as the unit tends to reset without warning when USB devices are plugged in. So if you are going to run an irlp-reinstall, I would suggest plugging your USB key with the backup file in before you boot the PC.
Boot your Pi, and perform the following steps in the config:
1) expand_rootfs Expand root partition to fill SD card
2) change_pass Change password for 'pi' user
3) change_locale Set locale (as required)
4) change_timezone Set timezone
5) memory_split Change memory split (set to 16)
6) ssh Enable ssh server
7) boot_behaviour DO NOT BOOT INTO DESKTOP
Then click Finish.
On initial boot, log in using user pi, and the password set above. The pi user is essentially a root user, and we want to create a root password, and carry on. That makes this more like other IRLP nodes...
At the prompt, type:
sudo su -
passwd root (set a password)
Now in the future, you can log in as root, or you can also choose to remove the pi user (optional):
userdel -r pi
NOTE: AT THIS POINT I REBOOTED THE Pi AND UNPLUGGED THE USB KEYBOARD.
I THEN INSERTED THE USB FLASH DRIVE WITH MY BACKUP FILES ON THEM.
I THEN USED PUTTY ON A SPARE COMPUTER TO FINISH THE IRLP INSTALL.
THIS WAS BECAUSE I WANTED THE SOUND CARD TO BE DETECTED WHILE INSTALLING
IRLP, AND DIDN'T WANT TO HOT PLUG THE FLASH DRIVE.
THE Pi ONLY HAS THE 2 USB PORTS. YMMV
INSTALLING THE IRLP SOFTWARE
Now we download the IRLP "get-irlp-files" script, which will carry us through the rest of the install.
chmod +x get-irlp-files
(This process will take several minutes (up to 20, but mine took closer to 45), as it basically strips the default install of about 200 unneeded packages, and configures your Pi for the packages it needs for IRLP to run).
Lets be honest - the Pi is not the fastest beast on the block.... so this process takes time.
Then progress with your install as usual. All of the commands are the same as a normal node, and the installer automatically picks up the special binary files for the ARM processor.
One nice thing now when restoring from a backup file, you have 2 options.
One is a regular back up install, and the second is a Fresh basic install.
I chose a Fresh Basic reinstall, so it was like I was starting over with an unmodified node.