copyfs-mount: 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/copyfs-mount - from package: copyfs

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

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