To start installing and using software from a Personal Package Archive, you first need to tell Ubuntu where to find the PPA.
$ sudo add-apt-repository ppa:cz.nic-labs/knot-dns $ sudo apt-get update $ sudo apt-get install knot
Running this sequence of commands will ensure that you will install Knot DNS on your system and keep it up-to-date in the future, when new versions are released.