piranha-passwd: 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 CentOS possible default full paths are:

/usr/sbin/piranha-passwd - from package: piranha

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

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