vboxmode: 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/vboxmode - from package: isdn4k-utils

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

On Debian possible default full paths are:

/usr/bin/vboxmode - from package: isdnvboxclient

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

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