Change swap size on start if needed

balenaOS now creates a /dev/zram0 device sized as min(25% of ram, 1G)
which on EtcherPro is 256M. We need 1G, so we resize it on start if
the amount is not 1G.
Also modprobe is no longer necessary as zram is built into the kernel.

Change-type: patch

Dockerfile

@@ -44,11 +44,6 @@ WORKDIR /usr/src/app/node_modules/.bin
 RUN ln -s ../electron/cli.js electron
 WORKDIR /usr/src/app
 
-RUN \
-	apt-get update \
-	&& apt-get install -y kmod \
-	&& rm -rf /var/lib/apt/lists/*
-
 CMD \
 	./zram.sh \
 	&& node /usr/src/app/update-config-and-start.js

docker-compose.yml

@@ -14,7 +14,6 @@ services:
     labels:
       io.balena.features.dbus: 1
       io.balena.features.supervisor-api: 1
-      io.balena.features.kernel-modules: 1
     volumes:
       - 'etcher_pki:/root/.pki'
       - 'etcher_cache:/root/.cache'

zram.sh

@@ -1,10 +1,13 @@
 #!/bin/bash
 
 DEVICE=/dev/zram0
+SIZE=1G
 
-if [ ! -b $DEVICE ]; then
+CURRENT_SIZE=$(zramctl --raw --noheadings --output DISKSIZE $DEVICE)
-	modprobe zram
+
-	zramctl $DEVICE --size 1024M
+if [ $CURRENT_SIZE != $SIZE ]; then
+	swapoff $DEVICE
+	zramctl $DEVICE --algorithm lz4 --size $SIZE
 	mkswap $DEVICE
 	swapon $DEVICE
 fi