pam_mount mounted encrypted partition gets automatically unmounted over time

[mondalaci]

/etc/crypttab :

storage /dev/sdb none luks, retry=1

/etc/security/pam_mount.conf.xml :

...
<volume path="/dev/sdb" mountpoint="/storage" cipher="aes-cbc-essiv:sha256" />
...

/storage gets mounted upon every reboot and it gets unmounted automatically about 20 minutes later. /dev/mapper/storage also disappears in such cases.

Nothing gets displayed by dmesg, I'm completely clueless as to why this happens.

Any advice is highly appreciated.

[mondalaci]

Forgot to mention but the mount point also gets removed in such cases.