From DSpace Wiki

[edit] Installing DSpace on Debian/testing Linux

You can use the Debian Packages for tomcat, postgres, and ant just fine. To get Java up and running, use the Debian package "java-package".

Download the java sdk from sun as usual, e.g., j2sdk-1_4_2_07-linux-i586.bin and do:

apt-get install fakeroot java-package
fakeroot make-jpkg j2sdk-1_4_2_07-linux-i586.bin
sudo dpkg -i sun-j2sdk1.4_1.4.2+07_i386.deb
apt-get install tomcat4 tomcat4-admin postgresql ant

This will install all necessary dependencies (a lot!) automatically. You can deinstall fakeroot and java-package; they are no longer needed.

There are three gotchas:

1. Edit /etc/default/tomcat4 to point to your java installation, e.g., /usr/lib/j2sdk1.4-sun.
2. Edit /etc/default/tomcat4 and set TOMCAT4_SECURITY=no, as tomcat has no access to dspace/config/dspace.cfg with enabled java security manager and will fail at loading dspace. Or if you are using Debian with Tomcat 5 you should edit /etc/init.d/tomcat5 with TOMCAT5_SECURITY=no.
3. Edit /etc/tomcat4/server.xml and comment the reference to tomcat-doc, unless you install tomcat4-webapps, too:

<!--Context path="/tomcat-docs" docase="tomcat-docs" debug="0">
<esources className="org.apache.naming.resources.FileDirContext"
allowLinking="true" />
</Context-->

Now you can install DSpace as usual, following the DSpace System Documentation.