ipcluster: 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/ipcluster - from package: python-ipython-console

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

On Debian possible default full paths are:

/usr/bin/ipcluster - from package: ipython

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

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