mdassembler: 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/mdassembler - from package: monodoc

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

On Debian possible default full paths are:

/usr/bin/mdassembler - from package: monodoc-base

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

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