netkit-ftp: 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

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/netkit-ftp - from package: ftp

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