diff --git a/install.sh b/install.sh
index 53bc95b..e29496e 100644
--- a/install.sh
+++ b/install.sh
@@ -123,17 +123,22 @@ init_installer_log() {
 }
 guard_existing_install_tree() {
   [[ $INSTALL_DIR = /* && $INSTALL_DIR != / ]] || return 0
-  INSTALL_PATH="$INSTALL_DIR" python3 - <<'PY' || die '安装目录路径不能包含符号链接'
+  INSTALL_DIR=$(INSTALL_PATH="$INSTALL_DIR" python3 - <<'PY'
 import os, pathlib
 p = pathlib.Path(os.environ['INSTALL_PATH'])
-cur = pathlib.Path(p.root)
-for part in p.parts[1:]:
-    cur /= part
-    if cur.exists() and cur.is_symlink(): raise SystemExit(1)
-if p.exists():
-    s = p.stat()
-    if os.geteuid() == 0 and (s.st_uid != 0 or s.st_mode & 0o022): raise SystemExit(2)
+print(p.resolve(strict=False))
 PY
+) || die '无法规范化安装目录路径'
+  [[ $INSTALL_DIR != / ]] || die '安装目录不能是根目录'
+  if [[ -e $INSTALL_DIR ]]; then
+    [[ -d $INSTALL_DIR && ! -L $INSTALL_DIR ]] || die '安装目录必须是普通目录'
+    INSTALL_PATH="$INSTALL_DIR" python3 - <<'PY' || die '安装目录权限不安全'
+import os, pathlib
+p = pathlib.Path(os.environ['INSTALL_PATH'])
+s = p.stat()
+if os.geteuid() == 0 and (s.st_uid != 0 or s.st_mode & 0o022): raise SystemExit(1)
+PY
+  fi
   [[ ! -e "$INSTALL_DIR/.env" || ! -L "$INSTALL_DIR/.env" ]] || die '.env must not be a symlink'
 }
 progress() {