grib_convert: 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/grib_convert - from package: grib_api

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

On Debian possible default full paths are:

/usr/bin/grib_convert - from package: libgrib-api-tools

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

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