ifenslave: 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/ifenslave - from package: iputils

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

On Debian possible default full paths are:

/sbin/ifenslave - from package: ifenslave

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

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