mmc-tool: 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/mmc-tool - from package: libcdio

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

On Debian possible default full paths are:

/usr/bin/mmc-tool - from package: libcdio-utils

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

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