ploop: 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/sbin/ploop - from package: ploop

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

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