httpd.itk: command not found

Have You tried accessing the binary with the full path?

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/sbin/httpd.itk - from package: httpd-itk

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