md5pass: 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/md5pass - from package: syslinux-perl

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

On Debian possible default full paths are:

/usr/bin/md5pass - from package: syslinux-utils

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

Error in other languages:
md5pass: bevel nie gevind nie
md5pass: comandă negăsită
md5pass: comando não encontrado
md5pass: commande introuvable
md5pass: command not found
md5pass: käsku ei ole
md5pass: không tìm thấy lệnh
md5pass: komanda nerasta
md5pass: Kommando nicht gefunden.
md5pass: kommandot finns inte
md5pass: komut yok
md5pass: nie znaleziono polecenia
md5pass: níor aimsíodh an t-ordú
md5pass: no se encontró la orden
md5pass: no s'ha trobat l'ordre
md5pass: opdracht niet gevonden
md5pass: parancs nem található
md5pass: perintah tidak ditemukan
md5pass: príkaz nenájdený
md5pass: příkaz nenalezen
md5pass: команда не найдена
md5pass: командата не е открита
md5pass: 命令找不到
md5pass: コマンドが見つかりません