rfkill: 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/rfkill - from package: rfkill

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

On Debian possible default full paths are:

/usr/sbin/rfkill - from package: rfkill

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

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