grdvolume: 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/grdvolume - 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/grdvolume - from package: GMT

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

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