vbox: 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 CentOS possible default full paths are:

/usr/bin/vbox - from package: isdn4k-utils

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/vbox - from package: isdnvboxclient

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

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