diff --git a/README.md b/README.md
index 80e05c7..b094a9f 100644
--- a/README.md
+++ b/README.md
@@ -59,7 +59,7 @@ chmod +x install.sh
 sudo ./install.sh
 ```
 
-脚本会把程序安装到 `/opt/server-monitor`，安装 `server-monitor.service`，并立即启动。默认监听 `0.0.0.0:8787`。
+脚本会把程序安装到 `/opt/server-monitor`，安装 `server-monitor.service`，并立即启动。默认监听 `0.0.0.0:8787`。如果仓库本身已经放在 `/opt/server-monitor`，脚本会跳过自我复制，可直接重复运行。
 
 ```bash
 systemctl status server-monitor --no-pager
@@ -226,4 +226,4 @@ sudo rm -f /etc/server-monitor.env
 ss -lntp | grep 8787
 ```
 
-改用 `--port` 或 systemd drop-in 修改端口。
+改用 `--port` 或 systemd drop-in 修改端口。
\ No newline at end of file
diff --git a/install.sh b/install.sh
index 79d41ee..1b4bf6a 100755
--- a/install.sh
+++ b/install.sh
@@ -22,17 +22,35 @@ if ! python3 -c 'import sys; raise SystemExit(0 if sys.version_info >= (3, 8) el
   exit 1
 fi
 
-SOURCE_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+SOURCE_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd -P)"
 TARGET_DIR="/opt/server-monitor"
 UNIT_PATH="/etc/systemd/system/server-monitor.service"
 ENV_PATH="/etc/server-monitor.env"
 
+for required in monitor.py servermon web deploy/server-monitor.service; do
+  if [[ ! -e "${SOURCE_DIR}/${required}" ]]; then
+    echo "安装文件不完整，缺少: ${SOURCE_DIR}/${required}" >&2
+    echo "请在完整仓库目录中运行安装脚本。" >&2
+    exit 1
+  fi
+done
+
 install -d -m 0755 "${TARGET_DIR}"
-install -m 0755 "${SOURCE_DIR}/monitor.py" "${TARGET_DIR}/monitor.py"
-rm -rf "${TARGET_DIR}/servermon" "${TARGET_DIR}/web"
-cp -a "${SOURCE_DIR}/servermon" "${TARGET_DIR}/servermon"
-cp -a "${SOURCE_DIR}/web" "${TARGET_DIR}/web"
-install -m 0644 "${SOURCE_DIR}/README.md" "${TARGET_DIR}/README.md"
+TARGET_DIR="$(cd "${TARGET_DIR}" && pwd -P)"
+
+if [[ "${SOURCE_DIR}" == "${TARGET_DIR}" ]]; then
+  # The repository is already installed at /opt/server-monitor (a common
+  # deployment). Copying a file onto itself would make install(1) fail and
+  # deleting the target directories would delete the source we are running
+  # from, so only install the systemd unit in this case.
+  echo "当前目录就是安装目录 ${TARGET_DIR}，跳过文件复制。"
+else
+  install -m 0755 "${SOURCE_DIR}/monitor.py" "${TARGET_DIR}/monitor.py"
+  rm -rf "${TARGET_DIR}/servermon" "${TARGET_DIR}/web"
+  cp -a "${SOURCE_DIR}/servermon" "${TARGET_DIR}/servermon"
+  cp -a "${SOURCE_DIR}/web" "${TARGET_DIR}/web"
+  install -m 0644 "${SOURCE_DIR}/README.md" "${TARGET_DIR}/README.md"
+fi
 
 if [[ ! -f "${ENV_PATH}" ]]; then
   cat >"${ENV_PATH}" <<'EOF'
@@ -55,4 +73,4 @@ echo "  状态:   systemctl status server-monitor --no-pager"
 echo "  日志:   journalctl -u server-monitor -f"
 echo "  认证:   编辑 ${ENV_PATH} 后 systemctl restart server-monitor"
 echo
-systemctl --no-pager --lines=0 status server-monitor.service || true
+systemctl --no-pager --lines=0 status server-monitor.service || true
\ No newline at end of file