isomaster: 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/isomaster - from package: isomaster

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

On Debian possible default full paths are:

/usr/bin/isomaster - from package: isomaster

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

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