clubak: 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/bin/clubak - from package: clustershell

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

On Debian possible default full paths are:

/usr/bin/clubak - from package: clustershell

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

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