Automatically resize the root filesystem if needed

2021-03-07 21:21:35 -08:00
parent 1f8a743f65
commit 55c0ec844e
6 changed files with 123 additions and 1 deletions
--- a/scripts/resize_root_fs.sh
+++ b/scripts/resize_root_fs.sh
@@ -0,0 +1,81 @@
+#!/bin/bash
+
+# Used by the OneFinity firmware to determine if the root filesystem
+# needs to be enlarged to maximize usage of the SD card.
+#
+# The majority of this code originates from /usr/lib/raspi-config/init_resize.sh
+
+get_fs_resize_variables () {
+    ROOT_PART_DEV=$(findmnt / -o source -n)
+    ROOT_PART_NAME=$(echo "$ROOT_PART_DEV" | cut -d "/" -f 3)
+    ROOT_DEV_NAME=$(echo /sys/block/*/"${ROOT_PART_NAME}" | cut -d "/" -f 4)
+    ROOT_DEV="/dev/${ROOT_DEV_NAME}"
+    ROOT_PART_NUM=$(cat "/sys/block/${ROOT_DEV_NAME}/${ROOT_PART_NAME}/partition")
+    BOOT_PART_DEV=$(findmnt /boot -o source -n)
+    BOOT_PART_NAME=$(echo "$BOOT_PART_DEV" | cut -d "/" -f 3)
+    BOOT_DEV_NAME=$(echo /sys/block/*/"${BOOT_PART_NAME}" | cut -d "/" -f 4)
+    ROOT_DEV_SIZE=$(cat "/sys/block/${ROOT_DEV_NAME}/size")
+    TARGET_END=$((ROOT_DEV_SIZE - 1))
+    PARTITION_TABLE=$(parted -m "$ROOT_DEV" unit s print | tr -d 's')
+    LAST_PART_NUM=$(echo "$PARTITION_TABLE" | tail -n 1 | cut -d ":" -f 1)
+    ROOT_PART_LINE=$(echo "$PARTITION_TABLE" | grep -e "^${ROOT_PART_NUM}:")
+    ROOT_PART_END=$(echo "$ROOT_PART_LINE" | cut -d ":" -f 3)
+}
+
+should_resize_root_partition() {
+    get_fs_resize_variables
+
+    ( set -o posix ; set )
+   
+    if [ "$BOOT_DEV_NAME" != "$ROOT_DEV_NAME" ]; then
+        FAIL_REASON="Boot and root partitions are on different devices"
+        return 1
+    fi
+
+    if [ "$ROOT_PART_NUM" -ne "$LAST_PART_NUM" ]; then
+        FAIL_REASON="Root partition should be last partition"
+        return 1
+    fi
+
+    if [ "$ROOT_PART_END" -gt "$TARGET_END" ]; then
+        FAIL_REASON="Root partition runs past the end of device"
+        echo $FAIL_REASON
+        return 1
+    fi
+
+    if [ ! -b "$ROOT_DEV" ] || [ ! -b "$ROOT_PART_DEV" ] || [ ! -b "$BOOT_PART_DEV" ] ; then
+        FAIL_REASON="Could not determine partitions"
+        return 1
+    fi
+
+    if [ "$ROOT_PART_END" -eq "$TARGET_END" ]; then
+        FAIL_REASON="Root partition is already expanded"
+        return 1
+    fi
+}
+
+if should_resize_root_partition; then
+    grep "init_resize" /boot/cmdline.txt >/dev/null
+    if [ $? -ne 0 ]; then
+        # On the next boot, init_resize.sh will:
+        #   Resize the root partition to use the rest of the SD card
+        #   Remove itself from /boot/cmdline.txt
+        #   Reboot the machine
+        sudo mount /boot -o rw,remount
+        sed -i 's/\(.*\)/\1 init=\/usr\/lib\/raspi-config\/init_resize.sh/' /boot/cmdline.txt
+    fi
+
+    # On the first boot after init_resize, resize2fs_once will:
+    #   Resize the root fs to fill its partition
+    #   Remove itself from the registered systemd services
+    #   Delete itself from the filesystem
+    #   Therefore, never run again
+    cp scripts/resize2fs_once /etc/init.d/resize2fs_once
+    chmod +x /etc/init.d/resize2fs_once
+    systemctl enable resize2fs_once
+
+    exit 0
+else
+    echo "Not resizing root partition: $FAIL_REASON"
+    exit 1
+fi