rubibtex: 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/rubibtex - from package: texlive

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

On Debian possible default full paths are:

/usr/bin/rubibtex - from package: texlive-lang-cyrillic

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

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