prosodyctl: command not found

Have You tried accessing the binary with the full path?

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/bin/prosodyctl - from package: prosody

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

On Debian possible default full paths are:

/usr/bin/prosodyctl - from package: prosody

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