realm: 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 Debian possible default full paths are:

/usr/sbin/realm - from package: realmd

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

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