Comment 2 for bug 1214009

Note that channel.ini is optional, and MUST live next to the chosen regular ini file. In practice, this means /etc/system-image/channel.ini lives next to /etc/system-image/client.ini, but be aware that if you use -C, the channel.ini file must live next to that configuration file.

If channel.ini does not exist, the old /etc/ubuntu-build file will be consulted, and the old defaults will be used. (I.e. it is not an error for channel.ini to be missing).