update-auctex-elisp: 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/sbin/update-auctex-elisp - from package: auctex

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

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