pvscan: 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:

/sbin/pvscan - from package: lvm2

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

On Debian possible default full paths are:

/sbin/pvscan - from package: lvm2

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

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