vzsplit: command not found

Have You tried accessing the binary with the full path?

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 Debian possible default full paths are:

/usr/sbin/vzsplit - from package: vzctl

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