md2html: 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/md2html - from package: nodejs-markdown

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

Error in other languages:
md2html: bevel nie gevind nie
md2html: comandă negăsită
md2html: comando não encontrado
md2html: commande introuvable
md2html: command not found
md2html: käsku ei ole
md2html: không tìm thấy lệnh
md2html: komanda nerasta
md2html: Kommando nicht gefunden.
md2html: kommandot finns inte
md2html: komut yok
md2html: nie znaleziono polecenia
md2html: níor aimsíodh an t-ordú
md2html: no se encontró la orden
md2html: no s'ha trobat l'ordre
md2html: opdracht niet gevonden
md2html: parancs nem található
md2html: perintah tidak ditemukan
md2html: príkaz nenájdený
md2html: příkaz nenalezen
md2html: команда не найдена
md2html: командата не е открита
md2html: 命令找不到
md2html: コマンドが見つかりません