snmptrapd: 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/sbin/snmptrapd - from package: net-snmp

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

On Debian possible default full paths are:

/usr/sbin/snmptrapd - from package: snmptrapd

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

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