mono-service: 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/mono-service - from package: mono-extras

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

On Debian possible default full paths are:

/usr/bin/mono-service - from package: mono-4.0-service

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

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