Add Upgrading Ubuntu as a linux til.

README.md

@@ -92,6 +92,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 ### linux
 
 - [Configure Your Server Timezone](linux/configure-your-server-timezone.md)
+- [Upgrading Ubuntu](linux/upgrading-ubuntu.md)
 
 ### mac
 

linux/upgrading-ubuntu.md

@@ -0,0 +1,15 @@
+# Upgrading Ubuntu
+
+I recently discovered that my Linode box was running a fairly old version of
+Ubuntu. Because it is a remote box that I SSH into, there is no graphical
+user interface. Upgrading to a newer release can be accomplished with the
+following command line utility:
+
+```
+$ do-release-upgrade
+```
+
+It includes a series of prompts regarding choices about the upgrade and a
+lot of waiting.
+
+Adding the `-d` flag will upgrade to the latest development release.