untex: command not found

Have You tried accessing the binary with the full path?

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/untex - from package: untex

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