nameif: 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/nameif - from package: net-tools

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

On Debian possible default full paths are:

/sbin/nameif - from package: net-tools

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

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