nova: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/nova - from package: python-novaclient

You may install the required package with command apt-get install {package}

Error in other languages:
nova: bevel nie gevind nie
nova: comandă negăsită
nova: comando não encontrado
nova: commande introuvable
nova: command not found
nova: käsku ei ole
nova: không tìm thấy lệnh
nova: komanda nerasta
nova: Kommando nicht gefunden.
nova: kommandot finns inte
nova: komut yok
nova: nie znaleziono polecenia
nova: níor aimsíodh an t-ordú
nova: no se encontró la orden
nova: no s'ha trobat l'ordre
nova: opdracht niet gevonden
nova: parancs nem található
nova: perintah tidak ditemukan
nova: príkaz nenájdený
nova: příkaz nenalezen
nova: команда не найдена
nova: командата не е открита
nova: 命令找不到
nova: コマンドが見つかりません