merb-specs: 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/merb-specs - from package: ruby-merb-core

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

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