pkaction: 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/pkaction - from package: polkit

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

On Debian possible default full paths are:

/usr/bin/pkaction - from package: policykit-1

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

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