guitarix: 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/guitarix - from package: guitarix

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

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