mount.posixovl: command not found

Have You tried accessing the binary with the full path?

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.posixovl - from package: fuse-posixovl

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