prefcnt: 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:

/usr/bin/prefcnt - from package: dwarves

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

On Debian possible default full paths are:

/usr/bin/prefcnt - from package: dwarves

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

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