ghdl: 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/ghdl - from package: ghdl

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

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