piranha_gui: 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/sbin/piranha_gui - from package: piranha

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