mk: 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/lib/plan9/bin/mk - from package: 9base

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

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