ml-makedepend: 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 Debian possible default full paths are:

/usr/bin/ml-makedepend - from package: smlnj
/usr/lib/smlnj/bin/ml-makedepend - from package: smlnj

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

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