ghc-pkg-7.0.4: 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-pkg-7.0.4 - from package: ghc-compiler

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

Error in other languages:
ghc-pkg-7.0.4: bevel nie gevind nie
ghc-pkg-7.0.4: comandă negăsită
ghc-pkg-7.0.4: comando não encontrado
ghc-pkg-7.0.4: commande introuvable
ghc-pkg-7.0.4: command not found
ghc-pkg-7.0.4: käsku ei ole
ghc-pkg-7.0.4: không tìm thấy lệnh
ghc-pkg-7.0.4: komanda nerasta
ghc-pkg-7.0.4: Kommando nicht gefunden.
ghc-pkg-7.0.4: kommandot finns inte
ghc-pkg-7.0.4: komut yok
ghc-pkg-7.0.4: nie znaleziono polecenia
ghc-pkg-7.0.4: níor aimsíodh an t-ordú
ghc-pkg-7.0.4: no se encontró la orden
ghc-pkg-7.0.4: no s'ha trobat l'ordre
ghc-pkg-7.0.4: opdracht niet gevonden
ghc-pkg-7.0.4: parancs nem található
ghc-pkg-7.0.4: perintah tidak ditemukan
ghc-pkg-7.0.4: príkaz nenájdený
ghc-pkg-7.0.4: příkaz nenalezen
ghc-pkg-7.0.4: команда не найдена
ghc-pkg-7.0.4: командата не е открита
ghc-pkg-7.0.4: 命令找不到
ghc-pkg-7.0.4: コマンドが見つかりません