diff --git a/index.js b/index.js
index 17867b8..a0f0a31 100644
--- a/index.js
+++ b/index.js
@@ -35,13 +35,13 @@ function getCpuPercent() {
 
 function getDisk() {
   try {
-    const out = execSync("df / --output=size,used,avail -B1", {
-      encoding: "utf-8",
-    });
-    const parts = out.trim().split("\n")[1].trim().split(/\s+/).map(Number);
-    const totalGB = +(parts[0] / 1e9).toFixed(1);
-    const usedGB = +(parts[1] / 1e9).toFixed(1);
-    const freeGB = +(parts[2] / 1e9).toFixed(1);
+    // Alpine df doesn't support --output, use standard POSIX format
+    const out = execSync("df -k /", { encoding: "utf-8" });
+    const parts = out.trim().split("\n")[1].trim().split(/\s+/);
+    // df -k columns: Filesystem, 1K-blocks, Used, Available, Use%, Mounted
+    const totalGB = +(parseInt(parts[1], 10) / 1e6).toFixed(1);
+    const usedGB = +(parseInt(parts[2], 10) / 1e6).toFixed(1);
+    const freeGB = +(parseInt(parts[3], 10) / 1e6).toFixed(1);
     const usagePercent = totalGB > 0 ? Math.round((usedGB / totalGB) * 100) : 0;
     return { totalGB, usedGB, freeGB, usagePercent };
   } catch {