I just recently upgraded to 12.10 Quantal, and now the /dev file system is not auto mounting correctly. The only issue that was caused by this, was openvpn could not create a tun device. I can look through the kern.log and see tun is loaded in the kernel. Again I was running the same kernel on 12.04 precise no problem. But in short I have no /dev/net folder, much less a /dev/net/tun that openvpn requires. After scratching my head for a while, I just tried a sudo mount /dev and presto, the tun adapter appeared in the /dev. I made a workaround, a custom upstart job to mount this file system and restart openvpn. I have tried three older kernels, and same thing happens. This is a 32bit machine running latest kernel. Also prior to mount /dev, it appears to be mounted. To the naked eye, all seem correct. It is not a empty filesystem, it just doesn't seem to have everything. Has anyone seen this before?

kern.log
kernel: tun: Universal TUN/TAP device driver, 1.6
kernel: tun: (C) 1999-2004 Max Krasnyansky <maxk@qualcomm.com>

cat /etc/fstab
proc /proc proc defaults 0 0
sys /sys sysfs defaults 0 0
/dev/xvda / ext3 defaults,user_xattr,acl 0 1
/dev/xvdb none swap defaults 0 0
dev /dev devtmpfs rw 0 0

Syslog:
openvpn-server_tcp[2898]: Note: Cannot open TUN/TAP dev /dev/net/tun: No such file or directory (errno=2)

Thanks.
Justin

I fixed my problem. I still do not know exactly what caused my issues, other than most of the upstart jobs were not starting. Since udev wasn't starting correctly, it probably caused the dev issue. I was getting strange errors on not being able to access files. I'm guessing something like the /var/run was missing. Since upstart is not the easiest thing to debug, and honestly could never figure out what file or directory it was trying to access. The only thing I did seem to notice was these init scripts seemed to be keying off runlevel. The ones that seem to run off dependency and emits events seemed to start fine. Anyways, once I noticed most of the upstart events were stopped, I immediately switched gears. I needed to add the --verbose to the kernel options, so I had to switch to the pv grub kernel to modify these settings. You have no control over the linode kernels. Strange thing happen, once I switched to the ubuntu kernel, the problem disappeared. The only real change that took place was me disabling a few boot options, the Xenify Distro, modules.dep Helper, automount dev was already disabled, and Disable updatedb is still yes. This is more or less changes need for the grub pv. I also had to disable ext3 write barriers, also a grub pv issue. I removed all my temporary upstart jobs and everything is working fine. I hate it when I fix something without knowing how I did it. I plan on leaving it in this configuration, as I did not know it was possible to run the ubuntu kernel until yesterday. Below is excerpts from the syslog.

Failed to spawn udev main process: unable to granpt: No such file or directory
Failed to spawn upstart-udev-bridge main process: unable to granpt: No such file or directory
Failed to spawn udev main process: unable to granpt: No such file or directory
Failed to spawn hwclock-save main process: unable to granpt: No such file or directory
Failed to spawn resolvconf post-stop process: unable to granpt: No such file or directory
Failed to spawn network-interface-security (networking) pre-start process: unable to granpt: No such file or directory
Failed to spawn networking pre-start process: unable to granpt: No such file or directory
Failed to spawn networking post-stop process: unable to granpt: No such file or directory
Failed to spawn cron main process: unable to granpt: No such file or directory
Failed to spawn dovecot pre-start process: unable to granpt: No such file or directory
Failed to spawn network-interface-security (networking) pre-start process: unable to granpt: No such file or directory
Failed to spawn networking pre-start process: unable to granpt: No such file or directory
Failed to spawn networking post-stop process: unable to granpt: No such file or directory
Failed to spawn network-interface-security (network-interface/tun1) pre-start process: unable to granpt: No such file or directory
Failed to spawn network-interface (tun1) pre-start process: unable to granpt: No such file or directory
Failed to spawn network-interface (tun1) post-stop process: unable to granpt: No such file or directory
Failed to spawn plymouth-stop pre-start process: unable to granpt: No such file or directory
Failed to spawn hwclock-save main process: unable to granpt: No such file or directory
Failed to spawn resolvconf post-stop process: unable to granpt: No such file or directory
Failed to spawn network-interface-security (network-interface/tun2) pre-start process: unable to granpt: No such file or directory

uname -a
Linux my-host 3.5.0-19-generic #30-Ubuntu SMP Tue Nov 13 17:49:53 UTC 2012 i686 i686 i686 GNU/Linux

Also I added the --no-log to the kernel options. I had to do it to a physical server, which controls upstart logging. I could not boot a physical server run 12.04 and this was a work around for a bug.