pyppd: 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/pyppd - from package: pyppd

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

On Debian possible default full paths are:

/usr/bin/pyppd - from package: pyppd

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

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