hp_synfast: 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/hp_synfast - from package: healpix

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

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