mixmaster: 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/mixmaster - from package: mixmaster

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

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