encode_keychange: 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/bin/encode_keychange - from package: net-snmp-utils

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

On Debian possible default full paths are:

/usr/bin/encode_keychange - from package: snmp

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

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