mount.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:

/sbin/mount.ploop - from package: ploop

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

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