Configuring the NavPi to use a USB drive as SWAP

If you are interested in using a USB drive as a swap space, this guide should get you sorted. Any size drive could be used, but for this guide we are using an 8GB USB drive. The drive is pre-formatted FAT32 but we’ll change it to EXT4.

Let’s get started

Backup your current NavPi img

Before proceeding with this swap configuration, it is worth making a backup image of your NavPi’s SD card so if it fails, you can easily restore to this point.

Backup your wallet.dat

To ensure you don’t lose any coins while making configuration changes to your NavPi, it’s essential to backup the wallet.dat file. This holds your private keys. With a backup of the wallet.dat you can always restore your wallet.

First, make sure your have encrypted your wallet. Then proceed with the following steps:

Open the WebUI
Go to control
Scroll down to security
Click Backup Wallet. This will download the wallet.dat file to your preferred device (USB, HD)
Save the wallet backup and rename it to wallet.dat

Insert drive

Connect USB drive to the NavPi

List drives connected to your NavPi

sudo blkid

Output
Device     Boot    Start     End   Sectors     Size    Id    Type
...
/dev/mmcb1k0p1: LABEL="boot" UUID="XXXX-XXXX" TYPE="vfat" PARTUUID="db06311d-01"
/dev/sda1: LABEL="UNTITLED" UUID="XXXX-XXXX" TYPE="vfat" PARTUUID="a9be7089-10"

You should see four entries, with the last one being your USB drive - dev/sda1

Format drive to EXT4

Your USB drive has mosty likely come preformatted as FAT, however you’ll get far more speed and reliability by using EXT4. FAT can be understood by Linux file system but is not native.

First unmount the USB

sudo umount /dev/sda1

Now reformat to ext4

sudo mkfs.ext4 /dev/sda1

Output
Writing superblocks and filesystem accounting information: done

Create mount directory

sudo mkdir /navswap

Ensure USB auto mounts on system boot

sudo nano /etc/fstab

When file is opened in nano, add the following line:

/dev/sda1    /navswap    ext4   nofail    0   0

Note: the ‘nofail’ mount option tells Raspbian to ignore this entry if the USB drive is not plugged in

ctrl + O to WriteOut the file, then press Enter, then ctrl + X to close nano

Set swap location and size

sudo nano /etc/dphys-swapfile

Set path to new swap:

CONF_SWAPFILE=/navswap/swap

Set new swap size:

CONF_SWAPSIZE=2048

In this example we’ll go for a 2GB swap

ctrl + O to WriteOut the file, then press Enter, then ctrl + X to close nano

Recreate and activate swap

sudo dphys-swapfile setup
sudo dphys-swapfile swapon

Output
[ok] Restarting dphys-swapfile (via systemctl): dyphys-swapfile.service.

Note: this might take awhile

Verify memory and new swap

free -m

Reboot your NavPi

sudo reboot

Verify new swap

cat /proc/swaps

Output
Filename         Type         Size      Used      Priority
/navswap/swap    file         2097418   0         -1

Check memory usage with swap in place

There are several options for checking memory use.

Built-in commands include:

free -h
top

pro tip - install htop - a nice option for monitoring interactively. It’s a nice way to filter on running processes, like ‘nav’. It combines the functionality of top and iotop into a single screen.

sudo apt-get install htop
htop

You should now see the swap drive being monitored.

Updated on 21 Mar 2019