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Enable ZRAM on the NavPi

The steps in this guide come from novaspirit’s repo rpi_zram and further information about ZRAM can be found here.

Novaspirit’s script will dynamically enable ZRAM on your current NavPi. It automatically detects the number of CPU cores to allocate to ZRAM computation, disables existing swap and enables ZRAM swap.

We have tested this on the NavPi devices and it does improve performance, though the USB swap solution seems to be superior if you are relying 100% on using the Chromium UI w/ Keyboard/Mouse connected to your NavPi.

If your current NavPi is running out of memory, ZRAM helps by expanding the amount of data you can store in RAM. It essentially buys you more time if you don’t have the USB swap enabled.

Let’s get started

Upgrade NavPi to latest version

See this guide for information on updating.

After updating, reboot your NavPi if you haven’t already.

sudo reboot

If update is successful you should now see the cfund directory appear in /home/stakebox/.navcoin4

cd /home/stakebox/.navcoin4
ls

Output
banlist.dat blocks cfund chainstate database db.log debug.log fee_estimates.dat navcoin.conf navcoin.pid peers.dat wallet.dat

Backup NavPi SD image

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 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:

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

Install zram script

This will download and copy the zram.sh script to your /usr/bin directory

sudo wget -O /usr/bin/zram.sh https://raw.githubusercontent.com/novaspirit/rpi_zram/master/zram.sh

Make script executable

sudo chmod +x /usr/bin/zram.sh

Ensure script runs on boot

echo '/usr/bin/zram.sh &' | sudo tee -a /etc/rc.local

Output
/usr/bin/zram.sh &

Reboot NavPi

sudo reboot

Check memory usage with ZRAM now configured

free -h

Output
          total      used      free     shared    buffers     cached
Mem:       923M      879M       43M         6M        22M        97M
-/+ buffers/cache:   760M      163M
Swap:       99M       29M       70M

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. It’s not a necessity, you can always just use free -h.

sudo apt-get install htop

htop

Updated on 21 Mar 2019