grun: 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/grun - from package: grun

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