pvdisplay: 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/pvdisplay - from package: lvm2

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

On Debian possible default full paths are:

/sbin/pvdisplay - from package: lvm2

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

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