swapon: add page (#1996)

pages/linux/swapon.md

@@ -0,0 +1,23 @@
+# swapon
+
+> Enables device or file for swapping.
+
+- Get swap information:
+
+`swapon -s`
+
+- Enable a given swap partition:
+
+`swapon {{/dev/sdb7}}`
+
+- Enable a given swap file:
+
+`swapon {{path/to/file}}`
+
+- Enable all swap areas:
+
+`swapon -a`
+
+- Enable swap by label of a device or file:
+
+`swapon -L {{swap1}}`