ardour3: 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/ardour3 - from package: ardour3

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

Error in other languages:
ardour3: bevel nie gevind nie
ardour3: comandă negăsită
ardour3: comando não encontrado
ardour3: commande introuvable
ardour3: command not found
ardour3: käsku ei ole
ardour3: không tìm thấy lệnh
ardour3: komanda nerasta
ardour3: Kommando nicht gefunden.
ardour3: kommandot finns inte
ardour3: komut yok
ardour3: nie znaleziono polecenia
ardour3: níor aimsíodh an t-ordú
ardour3: no se encontró la orden
ardour3: no s'ha trobat l'ordre
ardour3: opdracht niet gevonden
ardour3: parancs nem található
ardour3: perintah tidak ditemukan
ardour3: príkaz nenájdený
ardour3: příkaz nenalezen
ardour3: команда не найдена
ardour3: командата не е открита
ardour3: 命令找不到
ardour3: コマンドが見つかりません