ifconfig: 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:

/sbin/ifconfig - from package: net-tools

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

On Debian possible default full paths are:

/sbin/ifconfig - from package: net-tools

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

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