How to have a sorted list of your installed packages

When you want to install a new released version of your Linux system, it might be interesting to have a list of the installed packages you have in the previous version.

If you have a RPM-based distribution, all you have to do is:

rpm -qa | sort

How to fix buttons in Ubuntu 10.04

Thanks to the solution number 8 to this issue, I got the code to fix the left-oriented buttons in Ubuntu 10.04.

Here you have the code (it is only one line):

gconftool-2 --type string --set /apps/metacity/general/button_layout "menu:minimize,maximize,close"

Comparing PDF pages automatically

I needed to compare whether two PDF documents generated from the same TeX sources where different or not, since the generation method was slightly different for both.

Trying to compare it visually would be crazy, since the document contains more than 1400 pages. So I needed an automatic way to do it.

Albert Astals Cid from the poppler mailing list suggested to use pdftoppm and diff.

The way to automatically compare PDF pages was extremely easy: convert all pages to images, compare each pages and be warned only on the different ones.

After that, it only rests to check visually which differences contain those pages which have images that don’t match.

Doing arithmetic in TeX

I have just discovered accidentally how to perform simple arithmetic operations in TeX:

\number\numexpr 5+5\relax

And this will print the result, not the operands.

\include and \input

Thanks to this comment, I have realized the main difference between \include and \input in LaTeX: \include has a page break before and after the file and \input doesn’t.

Magnifying with XeTeX

When magnifying with XeTeX using the geometry package is important not to forget that the documentclass should not have the page size set on it, instead of having it set on the proper geometry option.

When openSUSE seems not be able to handle a DHCP connection

For some strange reason, my openSUSE 11.1 distribution seems not to be able to negotiate a DHCP Ethernet connection at home. Ubuntu 9.04 and Fedora 11 (live versions) are able to do that using the same computer and connections.

The only way it seemed to work was typing dhcpcd -k eth0 and after that dhcpcd -n eth0 (both as root). I don’t know what does it actually change, since I must keep that window open and the system considers that it isn’t connected.

It might be a bug, but sorry, too tricky to be reported.

How to generate a booklet from a PDF file

Using ConTeXt (taken from the imposition explanation):

\definepapersize	[filius][width=136mm, height=232mm]
\setuppapersize		[filius][A4,landscape]
\setuparranging		[2UP,doublesided]
\setuplayout [backspace=0pt,
    topspace=0pt,
       width=middle,
      height=middle,
    location=middle,
      header=0pt,
      footer=0pt,
      grid=no, marking=off]
\starttext
\insertpages
  [document.pdf][width=0pt]
\stoptext

You have to replace the document.pdf with the real file name and filius with the original paper size.

Searching for text in directories

To find which pure text files contains a given text from the command line, this is the proper command:

grep -ilr "pattern" directory

The -i option makes the search case-insensitive, -r searches the pattern recursively (that is, in the subdirectories that the actual directory might contain), and -l shows the file list where the pattern occurs.

Thanks to Juan Luis Belmonte for the tip (credit where credit is due).

Backing up all user data in Linux

One of the most I like most in Linux is the strong separation among user data and system data. This makes installing new versions, or moving data from different hard disks (and other sensitive operations that require all your data).

To copy all user data you need to type:

tar -cvpf compressed-file.tar /home/

This creates (-c) a file (-f) named compressed-file.tar retaining file and folder permissions and storing there all data from the /home/ directory.

To extract this you would only need to type:

tar -xf compressed-file.tar

The -x option specifies the extraction from -f (file).

To restore the data, the operation should be done at the root directory (since files will be extracted with full-path directories).