kde-config: 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

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/kde-config - from package: kdelibs3

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