How to Debug Debian Package

by yaobin.wen

Use the “Maintainer script flowcharts” to debug the installation scripts.

Debug Debian Package Installation

Today I was trying to use the oracle-java8-installer Debian package to install Java 8 to my Ubuntu 14.04.

Weirdly, the installation succeeded on some machines but failed on some others. The failure was caused by the unauthorized accesss to the target package. The oracle-java8-installer package uses wget to download the Java 8 installation file from Oracle’s official website. Oracle requires the user to agree the license before downloading, which is handled by the oracle-java8-installer. If the user agrees with the license, the installer downloads with the header Cookie: oraclelicense=a to indicate the license acceptance by the user. Then an AuthParam is appended to the URL:

http://download.oracle.com/otn-pub/java/jdk/8u181-b13/96a7b8442fe848ef90c96a2fad6ed6d1/jdk-8u181-linux-x64.tar.gz?AuthParam=1533080203_1cd7184c1597c2025098221ab6c8d57a

On those computers that failed, the AuthParam was missing, hence the unauthorized access error. Because the Java 8 installation file was not downloaded successfully, the installation would surely not succeed, either.

To debug this issue, I did the following things:

• Find the cached oracle-java8-installer package in /var/cache/apt/archives and copy it somewhere else for use.
• Uncompress the copy of the oracle-java8-installer package.
• Inside the extracted folder, you can find the DEBIAN sub-folder which has all the installation scripts: preinst, postinst, prerm, postrm, etc..
• Use sudo apt-get remove --purge oracle-java8-installer to completely remove the package from the system so the later calls of the installation scripts would have a clean system environment.
• Edit the installation scripts to add necessary debug messages.
• Use the Maintainer script flowcharts to go through the installation process and see what may go wrong.

More About oracle-java8-installer

The installer source code can be found here.

The direct cause of the installation (or downloading) failure was that, on the failed computers, the APT configuration has an http_proxy set and the download from Oracle’s website was not set as “DIRECT”. Once I set it as “DIRECT” download, the Java 8 installation file could be downloaded successfully.

The root cause seems to be the presence of http_proxy, which is usually the apt-cache-ng proxy, caused the AuthParam missing from the URL that wget uses. But I haven’t figured out why that happened.