gmixvm: 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/gmixvm - from package: mdk

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

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