Common Ubuntu Problems and Operations

An evolving record of common Ubuntu operations and problems I have encountered.

Ubuntu 12.04 laptop will not wake after suspend

A search suggested an NVIDIA driver problem. I first installed the driver through System Settings, but it did not support two monitors and could not be configured in NVIDIA Settings.

I then downloaded the newest driver from NVIDIA. After installation, the system froze at the Ubuntu startup screen. Newest is not always best; Ubuntu’s own choices are marked as tested by Ubuntu developers, although those had not worked for me either.

I returned to Nouveau, the open-source NVIDIA driver. Enter recovery mode—or press Ctrl+Alt+F1 in normal mode—remove all installed NVIDIA packages, and reinstall Xorg:

sudo apt-get purge nvidia*
sudo apt-get install xserver-xorg

GPG signature verification error

A typical error is:

W: GPG error: http://ppa.launchpad.net jaunty Release: The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY 21C022AA985E0E11

Copy the final eight characters after NO_PUBKEY, then run:

sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 985E0E11

Add or remove a PPA

A Personal Package Archive is a Launchpad service that builds uploaded source code into binary packages for use as an APT source. Its usual form is ppa:user/ppa-name.

Add one with:

sudo add-apt-repository ppa:user/ppa-name
sudo apt-get update

Remove it with:

sudo add-apt-repository -r ppa:user/ppa-name

Then remove its files under /etc/apt/sources.list.d and update again. For example, I had charles.list and charles.list.save; removing both files was sufficient.

Originally published on SegmentFault.