Problem: When running sudo apt-get update, you get a bunch of errors such as
W: GPG error: http://ppa.launchpad.net oneiric Release: The following signatures
couldn't be verified because the public key is not available: NO_PUBKEY 6E871C4A881574DE
And because of this, you can’t run the update. There are a couple of fixes for this.
First, there’s the standard suite of commands:
sudo apt-get clean
sudo rm -r /var/lib/apt/lists/*
sudo touch /var/lib/apt/lists/lock
sudo mkdir /var/lib/apt/lists/partial
sudo apt-get clean
sudo apt-get update
If these don’t work you may need to manually re-download the keys.
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys hex_key_here
Substituting the actually key for hex_key_here. The key is the long hexadecimal number at the end of the ap-get update error. Using the example I gave above, I would type into my terminal
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 6E871C4A881574DE
AND do yourself a favor and copy/paste the keys and/or the commands rather than manually typing them. One error is all it takes to make a lot of frustration.
If this stuff doesn’t work, there may be more info here: http://ubuntuforums.org/showthread.php?t=1221323
For shell themes:
Make sure the download is a .zip file. For some reason, that’s the only file type that Gnome-tweak recognizes. Then open gnome-tweak-tool (Advanced Settings) go to the Theme tab, and browse to find your theme.
For GTK/window themes:
Extract the folder containing the data into /usr/share/themes. Close and reopen gnome-tweak to add it to the options. If it still won’t show up, open a terminal and type
Go to desktop>gnome>shell>windows and type in the name of the theme (exactly!). Then do alt+F2 and it should reload, plus add it to your options in gnome-tweak.
For icon themes:
Extract the folder containing the icon data into /usr/share/icons. Restart gnome-tweak. They should be there.
Could not get lock /var/lib/apt/lists/lock- open (11: Resource temporarily unavailable)
Explanation of the problem:
Ubuntu uses the programs apt and dpkg for all package handling (installing, removing, updating, upgrading, etc.). To prevent multiple package management processes from running at once, apt or dpkg opens or “locks” an empty file named (appropriately) “lock”, in either
/var/lib/apt/lists/ (for apt processes) or
/var/lib/dpkg/ (for dpkg processes). If this file is already locked by an apt or dpkg process, no other process of that nature can run. That’s the in-depth explanation. Put shortly, you apparently have another apt or dpkg process running. This could be in the form of Synaptic Package Manager, or the USC, as they both utilize apt. Here’s brief instructions on how to remedy this.
Open a terminal and run
ps -ef | grep apt
The result will be a list of processes using apt. Kill them (all except the bottom one, called something like
cortman 3298 2798 0 15:40 pts/0 00:00:00 grep --color=auto apt
This is the grep process itself. To kill run
sudo kill -9 process_id
Substituting “process_id” for the actual id, which is a 4-5 digit number, second column from the left. If I were to kill the process given above, it would be
sudo kill -9 3298
Do the same for dpkg-
ps -ef | grep dpkg
to unlock the
/var/lib/dpkg/lock file. You can now run whatever installation process you were attempting before.
Glossary of terms:
ps -ef: lists all processes
grep apt: means “find processes with apt in the description”
sudo: run the following command as root
kill -9: end the process immediately and unconditionally.
First figure out which OS you’d like to be default. Observe its order number in the list of options (and note that GRUB starts counting at 0). Open a terminal and enter
sudo gedit /etc/default/grub
Change the GRUB_DEFAULT= to the number of the preferred OS. If my Ubuntu is third in the list (counting from zero, remember) I would set it to
Save, and then run
This should do it!