Isaac Sim 6.1.0: missing libxml2.so.2 on Ubuntu 26.04

[07LEE]

Following up on #656, as requested.

I’m seeing the same libxml2.so.2 loading error with Isaac Sim 6.1.0 (pip isaacsim==6.1.0.0) on Ubuntu 26.04. In my installation, readelf -d libfbxsdk.so shows that the bundled FBX SDK requires libxml2.so.2, while the extension’s libs/ directory contains libxml2.so.16 but no libxml2.so.2.
I understand that Ubuntu 26.04 is not currently supported. Is the older libxml2/libicu workaround still recommended for this environment, or are there plans to address this dependency in a future release?

[barry166]

Isaac Sim 6.1.0 does not currently list Ubuntu 26.04 as a supported host OS. The current requirements list Ubuntu 22.04/24.04, so the libxml2.so.2 failure is an unsupported-platform dependency mismatch rather than something pip install can reliably fix.

I would avoid replacing /usr/lib/libxml2.so.2 with a symlink to the bundled libxml2.so.16: those SONAMEs are not interchangeable, and changing the system library can break other applications. The safer options are:

1. run the pip package on a supported Ubuntu release (22.04 or 24.04), or
2. use the official Isaac Sim container on a supported Linux host, keeping the host libraries isolated.

If you must test on 26.04, treat installing a matching legacy libxml2 package inside an isolated environment/container as an unofficial workaround and expect it to be invalidated by future Isaac Sim updates. Please include the exact ldd/readelf output and the package build when reporting it upstream; the missing libxml2.so.2 dependency in libfbxsdk.so is the actionable detail for NVIDIA to fix.

[07LEE]

Thanks for the pointers. To clarify, I copied a compatible libxml2.so.2 build and its required dependencies into the extension’s asset_converter_native_bindings/libs/ directory. I did not modify system libraries or symlink .so.2 to .so.16.

The bundled libfbxsdk.so has the following DT_NEEDED entries, as reported by readelf -d:

 (NEEDED) Shared library: [libdl.so.2]
 (NEEDED) Shared library: [libpthread.so.0]
 (NEEDED) Shared library: [libxml2.so.2]
 (NEEDED) Shared library: [libz.so.1]
 (NEEDED) Shared library: [libstdc++.so.6]
 (NEEDED) Shared library: [libm.so.6]
 (NEEDED) Shared library: [libgcc_s.so.1]
 (NEEDED) Shared library: [libc.so.6]

Before applying the workaround, the only libxml2 files in the extension’s asset_converter_native_bindings/libs/ directory were:

libxml2.so
libxml2.so.16
libxml2.so.16.0.5

The library I supplied came from conda-forge’s libxml2 2.13.9 package (build h04c0eec_0, linux-64). After adding it and its dependencies, the reported extension-loading errors disappeared. FBX import/export was not tested.

I understand that Ubuntu 26.04 is not currently supported. Could the maintainers share any update following #656 on whether supplying a compatible legacy library remains the suggested workaround for this environment, or whether bundling or updating this dependency is planned for a future release?

[vick-yu]

We are checking with our team and will provide you with an update shortly.

[vick-yu]

An internal ticket (OMPE-110238) has been created to update libxml2 in the Autodesk forum.

[07LEE]

Thank you for checking and confirming that an internal ticket has been created for this issue. I appreciate the update!