ppi: 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/lib64/4ti2/bin/ppi - from package: 4ti2

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

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