mgd77convert: 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/mgd77convert - 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/mgd77convert - from package: GMT

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

Error in other languages:
mgd77convert: bevel nie gevind nie
mgd77convert: comandă negăsită
mgd77convert: comando não encontrado
mgd77convert: commande introuvable
mgd77convert: command not found
mgd77convert: käsku ei ole
mgd77convert: không tìm thấy lệnh
mgd77convert: komanda nerasta
mgd77convert: Kommando nicht gefunden.
mgd77convert: kommandot finns inte
mgd77convert: komut yok
mgd77convert: nie znaleziono polecenia
mgd77convert: níor aimsíodh an t-ordú
mgd77convert: no se encontró la orden
mgd77convert: no s'ha trobat l'ordre
mgd77convert: opdracht niet gevonden
mgd77convert: parancs nem található
mgd77convert: perintah tidak ditemukan
mgd77convert: príkaz nenájdený
mgd77convert: příkaz nenalezen
mgd77convert: команда не найдена
mgd77convert: командата не е открита
mgd77convert: 命令找不到
mgd77convert: コマンドが見つかりません