pkextract: 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/pkextract - from package: pktools

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

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