vfdecrypt: 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/vfdecrypt - from package: dmg2img

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

On Debian possible default full paths are:

/usr/bin/vfdecrypt - from package: dmg2img

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

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