vgmerge: 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/vgmerge - from package: lvm2

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

On Debian possible default full paths are:

/sbin/vgmerge - from package: lvm2

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

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