dnscache: 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/sbin/dnscache - from package: ndjbdns

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

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