e4defrag: add page (#4298)

pages/linux/e4defrag.md

@@ -0,0 +1,15 @@
+# e4defrag
+
+> Defragment an ext4 file system.
+
+- Defragment the file system:
+
+`e4defrag {{/dev/sdXN}}`
+
+- See how fragmented a file system is:
+
+`e4defrag -c {{/dev/sdXN}}`
+
+- Print errors and the fragmentation count before and after each file:
+
+`e4defrag -v {{/dev/sdXN}}`