monodoc-http: 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/monodoc-http - from package: monodoc-http

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

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