mpdrun: 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/bin/mpdrun - from package: mpich2

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

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