LowMem extension (for boards with < 256MB RAM)

extensions/lowmem.sh

@@ -0,0 +1,63 @@
+#!/usr/bin/env bash
+
+#
+# Armbian Optimizations for Low-Memory Boards
+#
+# Boards with less than *256MB* RAM need special optimizations to run Armbian smoothly.
+# This extension applies the necessary *userland* (not-kernel) optimizations
+# at build time.
+#
+
+function post_family_tweaks_bsp__copy_lowmem_config() {
+	display_alert "${EXTENSION}" "Installing default configuration" "debug"
+
+	# Copy /etc/default/armbian-lowmem configuration file
+	# Allows user to customize swapfile size / location
+	if [ ! -f "$destination/etc/default/armbian-lowmem" ]; then
+		install -m 664 "$SRC/packages/bsp/armbian-lowmem/etc/default/armbian-lowmem.dpkg-dist" "$destination/etc/default/armbian-lowmem"
+	fi
+
+	return 0
+}
+
+function post_family_tweaks_bsp__copy_lowmem_mkswap() {
+	local service_name="lowmem-mkswap"
+	# Devices with very low memory need a swapfile to operate smoothly (apt, locale-gen, etc)
+	display_alert "${EXTENSION}" "Installing ${service_name}.service" "debug"
+
+	# Copy systemd service and script to create swapfile
+	install -m 755 "$SRC/packages/bsp/armbian-lowmem/${service_name}.sh" "$destination/usr/bin/${service_name}.sh"
+	install -m 644 "$SRC/packages/bsp/armbian-lowmem/${service_name}.service" "$destination/lib/systemd/system/${service_name}.service"
+
+	return 0
+}
+
+function post_family_tweaks__enable_lowmem_mkswap() {
+	local service_name="lowmem-mkswap"
+	display_alert "${EXTENSION}" "Enabling ${service_name}.service" "debug"
+	chroot_sdcard systemctl enable "${service_name}.service"
+
+	return 0
+}
+
+function pre_umount_final_image__memory_optimize_defaults() {
+	local LOWMEM_TMPFS_RUN_MB=${LOWMEM_TMPFS_RUN_MB:-20}
+	# Optimize /etc/default settings to reduce memory usage
+	display_alert "${EXTENSION}" "Disabling ramlog by default to save memory" "debug"
+	sed -i "s/^ENABLED=.*/ENABLED=false/" "${MOUNT}"/etc/default/armbian-ramlog
+
+	display_alert "${EXTENSION}" "Disabling zram swap by default" "debug"
+	sed -i "s/^#\?\s*SWAP=.*/SWAP=false/" "${MOUNT}"/etc/default/armbian-zram-config
+
+	# /run is 10% of RAM by default
+	# systemd throws errors when <16MB is *free* in this partition
+	# during daemon-reload operations.
+	# Address with a fixed /run size of ${LOWMEM_TMPFS_RUN_MB}
+	if ! grep -qE "tmpfs[[:space:]]+/run[[:space:]]+tmpfs" "${MOUNT}/etc/fstab"; then
+		# Skip if /run entry already exists in fstab (userpatches, etc)
+		display_alert "${EXTENSION}" "Fixing /run size in /etc/fstab" "debug"
+		echo "tmpfs /run tmpfs rw,nosuid,nodev,noexec,relatime,size=${LOWMEM_TMPFS_RUN_MB}M,mode=755 0 0" >> "${MOUNT}"/etc/fstab
+	fi
+
+	return 0
+}

packages/bsp/armbian-lowmem/etc/default/armbian-lowmem.dpkg-dist

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+# configuration values for the armbian-lowmem extension
+# intended for use by boards with <256MB RAM
+#
+# swapfile path
+SWAPFILE_PATH=/swapfile
+#
+# size of swapfile to create in MiB
+SWAPFILE_SIZE_MB=256

packages/bsp/armbian-lowmem/lowmem-mkswap.service

@@ -0,0 +1,14 @@
+[Unit]
+Description=Armbian lowmem: Create a swapfile
+DefaultDependencies=no
+Wants=armbian-resize-filesystem.service
+After=armbian-resize-filesystem.service
+Before=basic.target
+
+[Service]
+Type=oneshot
+ExecStart=/usr/bin/lowmem-mkswap.sh
+RemainAfterExit=yes
+
+[Install]
+WantedBy=basic.target

packages/bsp/armbian-lowmem/lowmem-mkswap.sh

@@ -0,0 +1,35 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SWAPFILE_PATH="/swapfile"
+SWAPFILE_SIZE_MB=256
+
+[[ -f /etc/default/armbian-lowmem ]] && . /etc/default/armbian-lowmem
+
+echo "Creating swapfile of size ${SWAPFILE_SIZE_MB}MiB at ${SWAPFILE_PATH}"
+
+# Safety: do not overwrite existing swapfile
+if [[ -f "${SWAPFILE_PATH}" ]]; then
+    echo "Swapfile ${SWAPFILE_PATH} already exists, not overwriting." >&2
+    exit 0
+fi
+
+# Safety: ensure we have enough free space for the swapfile + headroom
+SWAPFILE_BASE=$(dirname "${SWAPFILE_PATH}")
+FREE_MB=$(df -Pm "${SWAPFILE_BASE}" | awk 'NR==2{print $4}')
+NEEDED_MB=$(( SWAPFILE_SIZE_MB + 64 ))  # 64MiB headroom
+if (( FREE_MB < NEEDED_MB )); then
+    echo "Not enough free space in ${SWAPFILE_BASE} to create ${SWAPFILE_SIZE_MB}MiB swapfile." >&2
+    exit 1
+fi
+
+# Create swapfile, set permissions, and enable it
+fallocate -l "${SWAPFILE_SIZE_MB}M" "${SWAPFILE_PATH}"
+chmod 600 "${SWAPFILE_PATH}"
+mkswap "${SWAPFILE_PATH}"
+# Add to fstab if not present
+if ! grep -qE "^[[:space:]]+${SWAPFILE_PATH}[[:space:]]+swap[[:space:]]" /etc/fstab; then
+  echo "${SWAPFILE_PATH} swap swap defaults,nofail,discard=once,pri=0 0 0" >> /etc/fstab
+fi
+
+swapon -p 0 "${SWAPFILE_PATH}"