Monday, March 11, 2013

Fun with Unicode Characters

Whenever I am tasked with creating a web page, it ends up being the absolute bare minimum.  (If you don't believe me, just visit!)  Of course I do it in the interest of fast rendering and bandwidth conservation... because I am a good Internet citizen.  So here are some fun unicode graphics that can be used as web page icons.  There are thousands of characters, but these seem to be a good cross platform sub-set.

And by the way: Excuse the font.
This -->  & an ampersand.
←←     ↑↑     →→     ↓↓    
↔↔     ↕↕    
⇐⇐     ⇑⇑     ⇒⇓     ⇓⇓    
⇔⇔     ⌂⌂    
■■     □□     ▪▪     ▫▫    
▲▲     ►►     ▼▼     ◄◄    
○○     ●●     ◖◖     ◘◘    
✇✇     ✈✈     ✓✓     ❥❥    
➲➲     ➳➳     ➸➸     ➼➼    

Wednesday, March 06, 2013

Removing Old Linux Kernels

Today, I had trouble removing an obsolete kernel from my workstation. It should have been simple enough, but I tried to use yum erase rather than rpm -e, and kept running into errors. That is obviously the bad news, so let's make sure to report the good news: YUM is such an improvement over RPM alone, that it is smart enough to know which kernels are obsolete. For instance:
# rpm -qa kernel
# uname -r
# yum erase kernel
kernel   x86_64   2.6.32-279.el6
kernel   x86_64   2.6.32-279.19.1.el6
Is this ok [y/N]:
First, we determine the machine has three kernels. Second, we see that that it is running the most recent version, dot-22. Finally, YUM demonstrates that it is smart enough to erase the two old kernels, but not the current kernel.

One small problem: I don't want to remove dot-19 because I have a driver problem with dot-22. I only want to remove dot-null. Here's the trick:
# yum list kernel
Loaded plugins: refresh-packagekit, security
Installed Packages
kernel.x86_64   2.6.32-279.el6
kernel.x86_64   2.6.32-279.19.1.el6
kernel.x86_64   2.6.32-279.22.1.el6
# yum erase kernel-2.6.32-279.el6
The critical success factors are to drop the arch and t0 add a dash(-) between the package name and the version number.