Ubuntu 14.04 Security update broke something

Question

I got a pop-up for a security update which uninstalled and reinstalled lots of stuff. During this it said something failed to update. Now when I try to install the update that failed I get this error message.

Check if you are using third party repositories. If so disable them, since they are a common source of problems. Furthermore run the following command in a Terminal: apt-get install -f

Running the command gives me this

Could not open lock file /var/lib/dpkg/lock - open (13: Permission denied)
Unable to lock the administration directory (/var/lib/dpkg/), are you root?

I barely know anything about linux so please give simple answers and don't use shorthand lingo.

Edit: I ran the command with sudo and got this in terminal

The following package was automatically installed and is no longer required:
  libllvm3.5
Use 'apt-get autoremove' to remove it.
The following extra packages will be installed:
  libllvm3.8v4
The following NEW packages will be installed:
  libllvm3.8v4
0 upgraded, 1 newly installed, 0 to remove and 9 not upgraded.
33 not fully installed or removed.
Need to get 0 B/10.2 MB of archives.
After this operation, 40.3 MB of additional disk space will be used.
Do you want to continue? [Y/n] y
(Reading database ... 788253 files and directories currently installed.)
Preparing to unpack .../libllvm3.8v4_1%3a3.8-2ubuntu3~trusty4_i386.deb ...
Unpacking libllvm3.8v4:i386 (1:3.8-2ubuntu3~trusty4) ...
dpkg: error processing archive /var/cache/apt/archives/libllvm3.8v4_1%3a3.8-2ubuntu3~trusty4_i386.deb (--unpack):
 trying to overwrite '/usr/lib/i386-linux-gnu/libLLVM-3.8.so.1', which is also in package libllvm3.8:i386 1:3.8~+rc3-1~exp1~gd~t
dpkg-deb: error: subprocess paste was killed by signal (Broken pipe)
Errors were encountered while processing:
 /var/cache/apt/archives/libllvm3.8v4_1%3a3.8-2ubuntu3~trusty4_i386.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)

Side note: I can't launch the Ubuntu software center and everytime I launch steam. Steam brings up the terminal and installs something every time it didn't used to do that.

Answer 1

You're getting the permission denied and are you root? prompts because you need to run the commands with elevated permissions. Place the prefix sudo in front of the commands so that the commands will be run under the root access.

Example:

$ sudo apt-get install -f

To execute the command I just gave you, type everything execept the dollar sign $. The dollar sign is specifying the prompt where you are typing the command.

That should clear the failed install by fixing the problems. It'll automatically load the available missing dependencies.