pvcreate: 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/pvcreate - from package: lvm2

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

On Debian possible default full paths are:

/sbin/pvcreate - from package: lvm2

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

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