mkroot: 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/share/Modules/bin/mkroot - from package: environment-modules

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

On Debian possible default full paths are:

/usr/bin/mkroot - from package: environment-modules

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

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