pwrkap_gtk: 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/pwrkap_gtk - from package: pwrkap-gui

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

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