rdmsr: 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/rdmsr - from package: msr-tools

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

On Debian possible default full paths are:

/usr/sbin/rdmsr - from package: msr-tools

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

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