genisoimage: 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/genisoimage - from package: genisoimage

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

On Debian possible default full paths are:

/usr/bin/genisoimage - from package: genisoimage

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

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