last message on the screen at shutdown is "Checking for running unattended-upgrades:"

Do you have any remote network shares mounted?

I also recently started getting this symptom on Ubuntu 11.04. where it hangs on shutdown at the line "Checking for running unattended-upgrades" for maybe 5 - 10 minutes, although it does eventually shutdown if you wait long enough. I found doing "shutdown -h now" on the terminal works immediately. It was only slow at shutting down when using the Ubuntu "Shutdown" menu option.

It started after I changed my network settings. I use wired Ethernet. I eventually discovered it seems to be something to do with having a remote network share and at what stage in the shutdown process Ubuntu decides to disconnect/disable the network.

I found two fixes:

1) If you dismount remote network shares prior to shutting down, it shuts down immediately. I have one CIFS share set to auto-mount at boot in my fstab.
2) In "Network Connections", I had the "Available to all users" check box unticked for my Ethernet card. As soon as I ticked this box, it started shutting down immediately without needing to manually dismount my CIFS share first.

It may be that the reason your shutdown stops there is because there are unattended upgrades in progress at the time, and so it waits for them to finish.

Your screenshot definitely shows two related bugs:

 - plymouth is failing to launch the splash screen for you. This is a bug in plymouth (though I don't know what might be causing it).
 - unattended-upgrades is configured to report the status of any running upgrades via plymouth, but this *isn't* where the "checking" message is sent, that message is sent to the console. Even though we want proper plymouth integration and we want the message to show on the splash at shutdown, unattended-upgrades should *also* send status to the console, for consistency there.

Status changed to 'Confirmed' because the bug affects multiple users.

This affects me as well. I'm running a clean install of Mythbuntu 12.04.

Could anybody experiencing this bug please post the contents of '/etc/apt/apt.conf.d/10periodic' on the system with the issue? Thanks in advance.

My 10periodic has the following lines:

APT::Periodic::Update-Package-Lists "1";
APT::Periodic::Download-Upgradeable-Packages "0";
APT::Periodic::AutocleanInterval "0";

The system is also a clean 12.04, running within a vbox.

Hi,
I a custom Ubuntu 12.04.4 I don't have it hanging but it is terribly slow to go to the next step. I also have

APT::Periodic::Update-Package-Lists "1";
APT::Periodic::Download-Upgradeable-Packages "0";
APT::Periodic::AutocleanInterval "0";

in the 10periodic file.