Red Hat Enterprise Linux

From these available sources several projects have created (largely) binary-compatible Linux distributions. These are available for free but come without formal support agreements, instead relying on self-help from the community via mailing lists. CentOS is the largest such distribution, Scientific Linux is another one aimed initially at HEP users (and several others like Whitebox Linux or CAOS Linux exist as well). Both CentOS and ScientificLinux aim to be userspace binary compatible with Red Hat, so will not replace/upgrade libraries, compilers or interpreters in the base distribution (although there may be add-on software package repositories that contain such updated versions, they are clearly marked as no longer being compatible, and are not available by default). These distributions also will fix any incompatibility between themselves and Red Hat (e.g. due to differences in the recompilation environments). In addition, these distributions will (have to) remove all references to Red Hat trademarks and logos.

In addition to the packages coming from Red Hat, ScientificLinux contains several additions that do not impact binary compatibility, such as OpenAFS (user space and kernel modules) or email clients such as pine. They also change the installer program (anaconda) to support locally-customized variants, so-called "sites".

ScientificLinuxCERN is such a variant (even if it does not use the "site"-mechanism from SL), it's aim to support CERN users and hardware. To this extend, CERN occasionally adds or replaces kernel drivers (which does not affect userspace compatibility), and adds programs that interface with CERN computing services (directory/printing/AFS/...) or hardware, including some proprietary ones that are only available on the CERN network (such as the ORACLE "instantclient" or hardware-specific utilities).

Last but not least, individual Linux services at CERN (such as LXPLUS or LXBATCH) contain often additional packages for monitoring or managing that are not part of the SLC distribution. They also may contain package sets that are not installed by default anywhere else (i.e. install more 32bit libraries on a 64bit machine than what a default Red Hat machine in "compatibility mode" would have, even if the individual packages would be available from Red Hat).

Responsibility:

• If an application does not work on SLC, but works on SL (or Red Hat), this is a problem for CERN Linux Support
• If an application does not work on SL, but works on Red Hat, this issue should be reported to upstream ScientificLinux.
• If an application works only on SLC (and neither on SL nor Red Hat), this is a problem for the package provider - typically they have established a dependency on some 3rd-party application that is not guaranteed to be available.