plug: 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/plug - from package: mustang-plug

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

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