tnftp: 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 CentOS possible default full paths are:

/usr/bin/tnftp - from package: tnftp

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/tnftp - from package: tnftp

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

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