twoftpd-anon: 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-anon - from package: twoftpd

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

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