in.tftpd: 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/sbin/in.tftpd - from package: tftp-server

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

On Debian possible default full paths are:

/usr/sbin/in.tftpd - from package: atftpd
/usr/sbin/in.tftpd - from package: tftpd-hpa
/usr/sbin/in.tftpd - from package: tftpd

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

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