purge_relay_logs: 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/purge_relay_logs - from package: mha4mysql-node

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

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