mkd2html: 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/bin/mkd2html - from package: discount

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

Error in other languages:
mkd2html: bevel nie gevind nie
mkd2html: comandă negăsită
mkd2html: comando não encontrado
mkd2html: commande introuvable
mkd2html: command not found
mkd2html: käsku ei ole
mkd2html: không tìm thấy lệnh
mkd2html: komanda nerasta
mkd2html: Kommando nicht gefunden.
mkd2html: kommandot finns inte
mkd2html: komut yok
mkd2html: nie znaleziono polecenia
mkd2html: níor aimsíodh an t-ordú
mkd2html: no se encontró la orden
mkd2html: no s'ha trobat l'ordre
mkd2html: opdracht niet gevonden
mkd2html: parancs nem található
mkd2html: perintah tidak ditemukan
mkd2html: príkaz nenájdený
mkd2html: příkaz nenalezen
mkd2html: команда не найдена
mkd2html: командата не е открита
mkd2html: 命令找不到
mkd2html: コマンドが見つかりません