telnet-probe: 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/libexec/pcp/bin/telnet-probe - from package: pcp

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

On Debian possible default full paths are:

/usr/lib/pcp/bin/telnet-probe - from package: pcp

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

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