prxs: 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/prxs - from package: proftpd-dev

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

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