First this may be bug #1464917:
If this affects you please go there and let them know by clicking the link "This affects me" above the intial bug report.
After the shutdown or reboot has hanged with this message.
Reached target Shutdown
You may only see this if you have removed the splash screen, if you don't see this message you can still try the following.
- Hold down the Alt and SysRq (Print Screen) keys.
- While holding those down, type the following keys in order, several
seconds apart: REISUB
- Computer should reboot.
Once it reboots immediately try shutdown button again, it should shutdown properly. Please add your name to the "This Affects Me" link at the launchpad bug site linked above.
You can also try the following after it hangs.
Try and login tty1 and reboot
- Write your username (lowercase, the name of the user folder in
/home) and hit Enter
- Write your password (nothing will appear) and hit Enter
If your password and username are correct, you are now logged in.
If that fails try
Ctrl+Alt+Del a couple times at that point in the tty1 screen.
You might see a message that states the machine is going to reboot and then it should do just that after a minute or so.
Its better than a hard boot - until its fixed.
In the bug notes it is reported that you can upgrade to Vivid-Proposed and it fixes the issue but some still see this after that upgrade. It might be worth a shot.