mountstats: command not found

Have You tried accessing the binary with the full path?

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/sbin/mountstats - from package: nfs-utils

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

On Debian possible default full paths are:

/usr/sbin/mountstats - from package: nfs-common

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