pifconfig: 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/pifconfig - from package: python-ethtool

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

On Debian possible default full paths are:

/usr/sbin/pifconfig - from package: python-ethtool

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

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