multiruby_setup: 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/multiruby_setup - from package: ruby-zentest

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

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