The Rules
  • Feel free to leave constructive criticism, or point out a better way to do something.
  • Personal attacks or flames, on me or anyone else, will be deleted.
  • Past history has shown that 99% of comments I can't read (i.e. those in other languages) to be spam. Therefore, any comment I can't read will be removed.
  • I'm pretty mellow concerning profanity, but excessive (as determined subjectively by me), bad language will be removed.

Friday, April 30, 2010

Downgrading packages in Arch Linux

On occasion (actually today was the first time) there is need to downgrade a package in Arch Linux. Yesterday I did a `pacman -Syu`, which upgraded gcc from 4.4.3 to 4.5.0. Today, I learned that 4.5.0 is unable to compile Moab. You'd think that a new release of your trusty compiler would work at least as good as the last one, but that's a topic (spelled R-A-N-T) for another day. When this catastrophe strikes, you can do the following to recover.

1. On my Arch system, package files are kept in /var/cache/pacman/pkg. Go there.

2. Find the desired package. In this particular case, /var/log/pacman.log told me that yesterday I upgraded from 4.4.3-2 to 4.5.0-1. So my working compiler up until yesterday was gcc 4.4.3.

3. "Upgrade" to the desired package: `pacman -U gcc-4.4.3-2-x86_64.pkg.tar.xz` and `pacman -U gcc-libs-4.4.3-2-x86_64.pkg.tar.xz`

4. Also in my case I'll want to stick with gcc 4.4.3 for a while now, so you can modify the IgnorePkg line in /etc/pacman.conf as follows:

IgnorePkg = gcc gcc-libs

This causes pacman to skip over gcc and gcc-libs when you do a system-wide upgrade (mine prints a warning to say it's being ignored, which I don't consider to be a bad thing).

Thursday, April 8, 2010

Terminal colors, all-day readability, and Arch Linux

A recent system upgrade broke my terminal colors. I don't know what exactly it was, or how it happened, but I opened a new terminal window, did a `ls`, and all my directories were bold and blue again. I personally find this difficult to read as I use a very dark blue background in my terminals (something on the order of #111133).

The solution:

Run the following command to create a default dir_colors file (the file that generates the colors for the ls command):

    `dircolors -p > ~/.dir_colors`
Then, add the following to your .bashrc file:
    # set the TERM variable to a color-enabled type (xterm-color)
export TERM="xterm-color"

# source my own .dir_colors file
if [ -f $HOME/.dir_colors ]
eval `dircolors -b $HOME/.dir_colors
This will allow you to customize what colors describe what objects for the ls command.

I personally make the following changes in ~/.dir_colors:
- DIR 01;34
+ DIR 00;36 # directories are cyan and non-bold
Then, I go through and turn off bold (swap 00 for 01) for almost everything. The only things I leave bold are executables and sym/hardlinks. For more info on dir_colors, see
    man dircolors
    man dir_colors