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11.

The most important concept to grasp is the Debian packaging system. In essence, large parts of your system should be considered under the control of the packaging system. These include: <itemizedlist> <listitem><para> <filename>/usr</filename> (excluding <filename>/usr/local</filename>) </para></listitem> <listitem><para> <filename>/var</filename> (you could make <filename>/var/local</filename> and be safe in there) </para></listitem> <listitem><para> <filename>/bin</filename> </para></listitem> <listitem><para> <filename>/sbin</filename> </para></listitem> <listitem><para> <filename>/lib</filename> </para></listitem> </itemizedlist> For instance, if you replace <filename>/usr/bin/perl</filename>, that will work, but then if you upgrade your <classname>perl</classname> package, the file you put there will be replaced. Experts can get around this by putting packages on <quote>hold</quote> in <command>aptitude</command>.

12.

One of the best installation methods is apt. You can use the command line version <command>apt-get</command> or full-screen text version <application>aptitude</application>. Note apt will also let you merge main, contrib, and non-free so you can have export-restricted packages as well as standard versions.

13.

Application Version Management

14.

Alternative versions of applications are managed by update-alternatives. If you are maintaining multiple versions of your applications, read the update-alternatives man page.

15.

Cron Job Management

16.

Any jobs under the purview of the system administrator should be in <filename>/etc</filename>, since they are configuration files. If you have a root cron job for daily, weekly, or monthly runs, put them in <filename>/etc/cron.{daily,weekly,monthly}</filename>. These are invoked from <filename>/etc/crontab</filename>, and will run in alphabetic order, which serializes them.

17.

On the other hand, if you have a cron job that (a) needs to run as a special user, or (b) needs to run at a special time or frequency, you can use either <filename>/etc/crontab</filename>, or, better yet, <filename>/etc/cron.d/whatever</filename>. These particular files also have an extra field that allows you to stipulate the user account under which the cron job runs.

18.

In either case, you just edit the files and cron will notice them automatically. There is no need to run a special command. For more information see cron(8), crontab(5), and <filename>/usr/share/doc/cron/README.Debian</filename>.

19.

Further Reading and Information

20.

If you need information about a particular program, you should first try <userinput>man <replaceable>program</replaceable></userinput>, or <userinput>info <replaceable>program</replaceable></userinput>.