vpcs: 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 Debian possible default full paths are:

/usr/bin/vpcs - from package: vpcs

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

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