sn: 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/sn - from package: mono-core

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

On Debian possible default full paths are:

/usr/bin/sn - from package: mono-devel

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

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