Mathabx is an important symbol library for latex. The full list of available symbols in latex can be found here. Following steps will help one to install mathabx in Ubuntu 9.04.

1. Download mathabx.zip from the following link.
2. $ unzip mathabx.zip
3. $ cd mathabx
4. $ sudo mkdir $TEXMF/fonts/source/public/mathabx
   In Ubuntu 9.04, TEXMF is /usr/share/texmf-texlive
5. sudo cp source/*.mf $TEXMF/fonts/source/public/mathabx
6. sudo cp texinputs/* $TEXMF/tex/generic/misc/
7. Update the database
   $ sudo texconfig rehash
8. Update the format file
   $ sudo fmtutil --refresh
   
9. When you build your tex document, you might get an error that /Asterisk is defined again - To avoid that, comment the line in mathabx.dcl where /Asterisk is defined.
   $ sudo gedit $TEXMF/tex/generic/misc/mathabx.dcl
   Search for line where /Asterisk is present in mathabx.dcl and put a % sign at the start of the line.
10. You are all set!
    

Use the command

$ crontab -e

In the editor window write

0 9 * * * /sbin/shutdown -h now

This will shutdown your computer at 9 hrs. After this restart cron service:

sudo /etc/init.d/cron restart

If you want to change the permissions of the file to 600 without affecting the directories permissions, use the following command:

find . ! -type d -exec chmod 600 {} \;