I upgraded my server PC’s Operating System from Ubuntu 12.04 LTS to 14.04 LTS on 18 Apr. 2014

When I upgraded it, “do-release-upgrade” didn’t work. So I put “-d” option.

$ sudo do-release-upgrade -d

I got troubles with the web server and with the mail server. The former is by the change of Apache’s specification(Upgrading to 2.4 from 2.2) and the latter was just my configuration files’ permission.