gresolver: 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/gresolver - from package: gresolver

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

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