telnet.netkit: 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/telnet.netkit - from package: telnet

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

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