openwrt_expand_root.sh — changes compared to the original-script (20260712)

• openwrt__docs-expand-root
• openwrt__original-script

Note

• This installation script requires ash or bash.
• The generated boot scripts remain POSIX-/bin/sh compatible.

changes

• Clean code / improved reusability
  • Code reorganized into functions
  • Added shebang (#!/bin/ash) and set -eu
  • Added comments
  • Improved code readability
    • Use of local variables
    • Paths are defined centrally and passed to functions
  • Replaced deprecated backticks with $(...)
  • Improved robustness
    • Idempotent registration for sysupgrade
    • Improved argument handling (-h|--help, error reporting for invalid options)
    • Removed non-portable awk -e usage (BusyBox-compatible)
• New feature
  • Optional size specification for the root partition (auto, %, M/MB, G/GB, GiB)
  • Input is validated and converted into a parted-compatible format
  • Strict size validation prevents command injection
• Bug fix
  • Instead of using a PARTUUID, the stable device name (e.g. /dev/mmcblk0p2) is now used in cmdline.txt
    • This ensures the system remains bootable after re-imaging or restoring OpenWrt backups