ftp-proxy: command not found

Have You tried accessing the binary with the full path?

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/sbin/ftp-proxy - from package: ftp-proxy

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