mountpoint: 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:

/bin/mountpoint - from package: sysvinit-tools

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

On Debian possible default full paths are:

/bin/mountpoint - from package: initscripts

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

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