twoftpd-conf: 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/twoftpd-conf - from package: twoftpd

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

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