mmldif-bin: 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/mmldif-bin - from package: 389-ds-base

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

On Debian possible default full paths are:

/usr/bin/mmldif-bin - from package: 389-ds-base

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

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