CentOS 5.11, with GCC 5.2 built on top. Includes Miniconda and some fundamental tools for building packages in the conda ecosystem.
There are helpful starter scripts at https://github.com/ContinuumIO/docker-images/tree/master/conda_builder_linux that help set environment variables for 32 or 64-bit builds, as well as the C++ ABI. If you do not use these scripts, your builds will default to 64-bit, with the new GCC 5 (C++11) ABI.
Code and more details are at:
Note on tag versioning:
<CentOS version>-<GCC version>-<build number of CentOS/GCC base image>-<build number of this image>
Build number of this image will change for things like updating miniconda, conda-build, or other such tools. First 3 version entries only reflect base image from https://hub.docker.com/r/continuumio/centos5_gcc5_base/ that this image builds on.