jruby: 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/jruby - from package: jruby
/usr/lib/jruby/bin/jruby - from package: jruby

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

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