isovfy: 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/isovfy - from package: genisoimage

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

On Debian possible default full paths are:

/usr/bin/isovfy - from package: genisoimage

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

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