ppserver: 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/ppserver - from package: python-pp

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

On Debian possible default full paths are:

/usr/bin/ppserver - from package: python-pp

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

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