ghc: 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/ghc - from package: ghc-compiler

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

On Debian possible default full paths are:

/usr/bin/ghc - from package: ghc
/usr/lib/ghc/bin/ghc - from package: ghc

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

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