cowpoke: 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/cowpoke - from package: devscripts

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

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