exrnlm: 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/exrnlm - from package: exrtools

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

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