Long overdue first commit with content

content/en/blog/commands/rrdtool.md

@@ -0,0 +1,21 @@
+---
+title: "rrdtool"
+linkTitle: "rrdtool"
+date: 2018-09-25
+description: >
+  rrdtool
+---
+
+## Graph manually
+
+{{< highlight sh >}}
+for i in `ls`; do
+    rrdtool graph $i.png -w 1024 -h 768 -a PNG --slope-mode --font DEFAULT:7: \
+      --start -3days --end now DEF:in=$i:netin:MAX DEF:out=$i:netout:MAX \
+      LINE1:in#0000FF:"in" LINE1:out#00FF00:"out"
+done
+{{< /highlight >}}
+
+## References
+
+- https://calomel.org/rrdtool.html