I have a network share mounted with cifs which does not work as expected. It should automount at boot and dismount at shutdown. It does not automount at boot, but "# mount -a" will mount it in the gui after booting finishes. This I can live with, but at shutdown or reboot, the cifs share hangs for about 30 seconds before dying. My /etc/fstab entry I saw a bug report about the cifs umount issue, but can't find it at the moment. I did notice that it was a very old bug. If I remember to do "# umount /media/data-srv" before rebooting, all is fine, but I seem to constantly forget and then stew as the system hangs for an extra 30-45 seconds. I've tried several things to automate it including shutdown scripts added to /etc/init.d/ and elsewhere, but nothing seems to work. Anyone have this issue and find a work-around?

30 seconds is such a big problem ?
As for mounting at boot, see this post.

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If you use the _netdev option, mounting the share will be deferred until the network is ready.

As to the time it takes to unmount, it may depend partly on how the share is mounted and how the device at the server is mounted. The async option allows asyncronous updates & caching. This will improve performance while you are using the device but unsynced data needs to be written to the device before it can be umounted.

30 seconds may be a time-out value for something that is failing. The kernel logs or samba logs may indicate the cause. If you can correct, you may be able to umount the drive quicker.

You might also look at configuring automount. This will automatically mount directories when you enter them and unmount them if you haven't used them for a while. In other words, the directory may be unmounted already, so if you are shutting down for example, you won't have a delay.