Ubuntu 16.04 LTS is available now. Unfortunately, standard way for upgrading is not worked for me. Here I'll show dirty way to upgrade Ubuntu installation that works for me.
Note. After upgrading to Ubuntu 16.04 I found one more option on askubuntu.com. I'll try it in future.
The standart way for upgrading from command line is to use
sudo apt-get update sudo apt-get upgrade sudo apt-get dist-upgrade sudo update-manager -d # upgrade with GUI
sudo do-release-upgradecommand is also possible to start upgrading in terminal without GUI.
In my case last command was failed with mysterious error:
Could not calculate the upgrade An unresolvable problem occurred while calculating the upgrade. This can be caused by: * Upgrading to a pre-release version of Ubuntu * Running the current pre-release version of Ubuntu * Unofficial software packages not provided by Ubuntu If none of this applies, then please report this bug using the command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal.
It seemed that error message was about some
apt-sources that I need to disable. But disabling didn't help.
I upgraded successfully with commands:
sudo sed -i 's/wily/xenial/g' /etc/apt/sources.list sudo apt-get update sudo apt-get dist-upgrade
I'm not sure 100% of the correctness of this approach, but it works for me.