grdreformat: 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 CentOS possible default full paths are:

/usr/bin/grdreformat - from package: GMT

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/lib/gmt/bin/grdreformat - from package: GMT

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

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