grdinfo: 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/grdinfo - 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/grdinfo - from package: GMT

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

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