rb_test: 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/lib/ctdb/tests/bin/rb_test - from package: ctdb-dbg

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

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