dirac_unittest: 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/dirac_unittest - from package: dirac

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

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