ftpd: 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/kerberos/sbin/ftpd - from package: krb5-appl-servers

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

On Debian possible default full paths are:

/usr/sbin/ftpd - from package: inetutils-ftpd

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

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