mkbiarch: 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/mkbiarch - from package: livecd-tools

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

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