mongosniff: 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/mongosniff - from package: mongodb

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

On Debian possible default full paths are:

/usr/bin/mongosniff - from package: mongodb-clients

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

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