rrdcached: 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 Debian possible default full paths are:

/usr/bin/rrdcached - from package: rrdcached

You may install the required package with command apt-get install {package}

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