snmpwalk: 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/snmpwalk - 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/snmpwalk - from package: snmp

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

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