How do I upgrade to the development release (aka. Ubuntu+1)?

The truly command line way is (e.g. if you don't have a gui):

sudo do-release-upgrade -d

where -d means update to a development version

do-release-upgrade [options]

DESCRIPTION

   Upgrade  the  operating system to the latest release from the command-line.
   This is the preferred command if the machine has no graphic environment
   or if the machine is to be upgraded over a remote connection.

OPTIONS

   -h, --help
          show help message and exit

   -d, --devel-release
          Check if upgrading to the latest devel release is possible

Press Alt + F2 and type update-manager -d. On the top of the window you will see an info of the new Ubuntu+1 "release".

However, upgrading to a development release is not recommended, as it is a unstable release.

See this question for tips when you have problems: There's an issue with an Alpha/Beta Release of Ubuntu, what should I do?

There are two ways to upgrade:

• Upgrade using update-manager
• Upgrade using alternate cd

However note it is not recommended to upgrade it to Ubuntu+1, since it is not stable.

Upgrade using update-manager:

Press Alt+F2 and then type update-manager -d. When update manager appears then click on upgrade.

Upgrade using alternate cd:

You can also upgrade using the alternate cd. After downloading the latest build then press Alt+F2 and enter gksu /cdrom/cdromupgrade.

Because it is a development release, you will almost certainly have problems. See: There's an issue with an Alpha Release of Ubuntu, what should I do?