ap-tftp: 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/ap-tftp - from package: ap-utils

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

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