Online / 6 & 7 February 2021


XALT: Lessons from attaching to almost every program in Linux

XALT is a tool run on clusters to find out what programs and libraries are run. XALT uses the environment variable LD_PRELOAD to attach a shared library to execute code before and after main(). This means that the XALT shared library is a developer on every program run under linux. This shared library is part of every program run. This talk will discuss the various lessons about routine names and memory usage. Adding XALT to track container usage presents new issues because of what shared libraries are available in the container.

XALT is an open source project under the LGPL licence. It is available at and the documentation can be found at A presentation can be found at:


Robert McLay