subdownloader: 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/subdownloader - from package: subdownloader

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

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