Chapter 1. Red Hat Software Collections 2.0

This chapter serves as an overview of the Red Hat Software Collections 2.0 content set. It provides a list of components and their descriptions, sums up changes in this version, documents relevant compatibility information, and lists known issues.

1.1. About Red Hat Software Collections

For certain applications, more recent versions of some software components are often needed in order to use their latest new features. Red Hat Software Collections is a Red Hat offering that provides a set of dynamic programming languages, database servers, and various related packages that are either more recent than their equivalent versions included in the base Red Hat Enterprise Linux system, or are available for this system for the first time. For a complete list of components that are distributed as part of Red Hat Software Collections and a brief summary of their features, see Section 1.2, “Main Features”.
Red Hat Software Collections does not replace the default system tools provided with Red Hat Enterprise Linux 6 or Red Hat Enterprise Linux 7. Instead, a parallel set of tools is installed in the /opt/ directory and can be optionally enabled per application by the user using the supplied scl utility. The default versions of Perl or PostgreSQL, for example, remain those provided by the base Red Hat Enterprise Linux system.
All Red Hat Software Collections components are fully supported under Red Hat Enterprise Linux Subscription Level Agreements, are functionally complete, and are intended for production use. Important bug fix and security errata are issued to Red Hat Software Collections subscribers in a similar manner to Red Hat Enterprise Linux for at least three years from the release of each major version. A new major version of Red Hat Software Collections is released approximately every 18 months, and in each major release stream, each version of a selected component remains backward compatible. For detailed information about length of support for individual components, refer to the Red Hat Software Collections Product Life Cycle document.
Red Hat Developer Toolset is now part of Red Hat Software Collections, included as a separate Software Collection. For more information about Red Hat Developer Toolset, refer to the Red Hat Developer Toolset Release Notes and the Red Hat Developer Toolset User Guide.

1.2. Main Features

Red Hat Software Collections 2.0 provides recent stable versions of the tools listed in Table 1.1, “Red Hat Software Collections 2.0 Components”.

Table 1.1. Red Hat Software Collections 2.0 Components

Component Software Collection Description
Red Hat Developer Toolset 3.1 devtoolset-3 Red Hat Developer Toolset is designed for developers working on the Red Hat Enterprise Linux platform. It provides current versions of the GNU Compiler Collection, GNU Debugger, Eclipse development platform, and other development, debugging, and performance monitoring tools. For a complete list of components, see the Red Hat Developer Toolset Components table in the Red Hat Developer Toolset User Guide.
Perl 5.20.1 rh-perl520 A release of Perl, a high-level programming language that is commonly used for system administration utilities and web programming. The rh-perl520 Software Collection provides additional utilities, scripts, and database connectors for MySQL and PostgreSQL. Also, it includes the DateTime Perl module and the mod_perl Apache httpd module, which is supported only with the httpd24 Software Collection.
PHP 5.4.40 php54 A release of PHP with PEAR 1.9.4 and a number of additional extensions. PHP 5.4 provides a number of language and interface improvements. The memcache and Zend OPcache extensions are also included.
PHP 5.5.21 php55 A release of PHP with PEAR 1.9.4 and enhanced language features including better exception handling, generators, and Zend OPcache. The memcache and mongodb extensions are also included.
PHP 5.6.5 rh-php56 A release of PHP with PEAR 1.9.5 and enhanced language features including constant expressions, variadic functions, arguments unpacking, and the interactive debugger. The memcache, mongo, and XDebug extensions are also included.
Python 2.7.8 python27 A release of Python 2.7 with a number of additional utilities. This Python version provides various new features and enhancements, including a new ordered dictionary type, faster I/O operations, and improved forward compatibility with Python 3. The python27 Software Collections contains the Python 2.7.8 interpreter, a set of extension libraries useful for programming web applications and mod_wsgi (only supported with the httpd24 Software Collection), MySQL and PostgreSQL database connectors, and numpy and scipy.
Python 3.4.2 rh-python34 A release of Python 3 with a number of additional utilities. This Software Collection gives developers on Red Hat Enterprise Linux access to Python 3 and allows them to benefit from various advantages and new features of this version. The rh-python34 Software Collection contains Python 3.4.2 interpreter, a set of extension libraries useful for programming web applications and mod_wsgi (only supported with the httpd24 Software Collection), PostgreSQL database connector, and numpy and scipy.
Ruby 2.2.2 rh-ruby22 A release of Ruby 2.2. This version provides substantial performance and reliability improvements, including incremental and symbol garbage collection and many others, while maintaining source level backward compatibility with Ruby 2.0.0 and Ruby 1.9.3.
Ruby on Rails 4.1.5 rh-ror41 A release of Ruby on Rails 4.1, a web application development framework written in the Ruby language. This version provides a number of new features including Spring application preloader, config/secrets.yml, Action Pack variants, and Action Mailer previews. This Software Collection is supported together with the rh-ruby22 Collection.
MariaDB 10.0.17 rh-mariadb100 A release of MariaDB, an alternative to MySQL for users of Red Hat Enterprise Linux. For all practical purposes, MySQL is binary compatible with MariaDB and can be replaced with it without any data conversions. This version adds the PAM authentication plugin to MariaDB.
MongoDB 2.6.9 rh-mongodb26 A release of MongoDB, a cross-platform document-oriented database system classified as a NoSQL database. This Software Collection includes the mongo-java-driver package.
MySQL 5.6.24 rh-mysql56 A release of MySQL, which provides a number of new features and enhancements, including improved performance.
PostgreSQL 9.4.1 rh-postgresql94 A release of PostgreSQL, which provides a number of enhancements, including improved scalability (bi-directonal replication, cascading replication), increased flexibility of native JSON support, and improved performance.
Node.js 0.10 nodejs010 A release of Node.js with npm 1.4.28 and support for the SPDY protocol version 3.1. This Software Collection gives users of Red Hat Enterprise Linux access to this programming platform.
nginx 1.6.2 nginx16 A release of nginx, a web and proxy server with a focus on high concurrency, performance and low memory usage. This version introduces a number of new features, including various SSL improvements, support for SPDY 3.1, cache revalidation with conditional requests, and authentication request module.
Apache httpd 2.4.12 httpd24 A release of the Apache HTTP Server (httpd), including a high performance event-based processing model, enhanced SSL module and FastCGI support. The mod_auth_kerb module is also included.
Thermostat 1.2.0 thermostat1 A release of Thermostat, a monitoring and instrumentation tool for the OpenJDK HotSpot JVM, with support for monitoring multiple JVM instances. This Software Collection depends on the rh-mongodb26 and rh-java-common components.
DevAssistant 0.9.3 devassist09 A release of DevAssistant, a tool designed to assist developers with creating and setting up basic projects in various programming languages, installing dependencies, setting up a development environment, and working with source control. DevAssistant supports the C, C++, Java, and Python programming languages but it is able to support working with any other language, framework, or tool due to its modular architecture.
Maven 3.0.5 maven30 A release of Maven, a software project management and comprehension tool used primarily for Java projects. Based on the concept of a project object model (POM), Maven can manage a project's build, reporting, and documentation from a central piece of information.
Passenger 4.0.50 rh-passenger40 A release of Phusion Passenger, a web and application server, designed to be fast, robust, and lightweight. It supports Ruby using the ruby193, ruby200, or rh-ruby22 Software Collections together with Ruby on Rails using the ror40 or rh-ror41 Collections. It can also be used with nginx 1.6 from the nginx16 Software Collection and with Apache httpd from the httpd24 Software Collection.
Common Java Packages 1.1 rh-java-common This Software Collection provides common Java libraries and tools used by other collections. The rh-java-common Software Collection is required by the devtoolset-3, maven30, rh-mongodb26, and thermostat1 components.
V8 3.14.5.10 v8314 This Software Collection provides the V8 JavaScript engine and is supported only as a dependency for the mongodb24, rh-mongodb26, ruby193, ror40, rh-ror41, and nodejs010 Software Collections.
Previously released Software Collections remain available in the same distribution channels. For example, the git19 Software Collection, which provides Git 1.9.4, has not been updated since Red Hat Software Collections 1.2 but still can be installed along with the Red Hat Software Collections 2.0 components or other previously released components.
All currently available Software Collections are listed in the Table 1.2, “All Available Software Collections”. For detailed information regarding components that have not been updated since Red Hat Software Collections 1, refer to the Red Hat Software Collections 1.2 Release Notes. See the Red Hat Software Collections Product Life Cycle document for information on the length of support for individual components.

Table 1.2. All Available Software Collections

Component Software Collection
Components New in Red Hat Software Collections 2.0
Perl 5.20.1rh-perl520
PHP 5.6.5rh-php56
Python 3.4.2rh-python34
Ruby 2.2.2rh-ruby22
Ruby on Rails 4.1.5rh-ror41
MariaDB 10.0.17rh-mariadb100
MongoDB 2.6.9rh-mongodb26
MySQL 5.6.24rh-mysql56
PostgreSQL 9.4.1rh-postgresql94
Passenger 4.0.50rh-passenger40
Common Java Packages 1.1rh-java-common
Components Updated in Red Hat Software Collections 2.0
Red Hat Developer Toolset 3.1devtoolset-3
PHP 5.4.40php54
PHP 5.5.21php55
Python 2.7.8python27
Node.js 0.10nodejs010
nginx 1.6.2nginx16
Apache httpd 2.4.12httpd24
Thermostat 1.2.0thermostat1
DevAssistant 0.9.3devassist09
Maven 3.0.5maven30
V8 3.14.5.10v8314
Components Not Updated since Red Hat Software Collections 1
Git 1.9.4git19
Perl 5.16.3perl516
Python 3.3.2python33
Ruby 1.9.3ruby193
Ruby 2.0.0ruby200
Ruby on Rails 4.0.2ror40
MariaDB 5.5.37mariadb55
MongoDB 2.4.9mongodb24
MySQL 5.5.37mysql55
PostgreSQL 9.2.8postgresql92

1.3. Changes in Red Hat Software Collections 2.0

1.3.1. Overview

New Software Collections

Red Hat Software Collections 2.0 adds these new Software Collections:

Updated Software Collections

The following components have been updated in Red Hat Software Collections 2.0:
The further detailed sections describe changes since Red Hat Software Collections 1.2.

1.3.2. Changes in Red Hat Developer Toolset

Red Hat Software Collections 2.0 is released with Red Hat Developer Toolset 3.1. The following components have been upgraded in this release:
  • Eclipse to version 4.4.2
  • GCC to version 4.9.2
  • elfutils to version 0.161
  • GDB to version 7.8.2
  • SystemTap to version 2.6
  • Valgrind to version 3.10.1
  • Dyninst to version 8.2.1
The Red Hat Developer Toolset 3.1 release also includes a bug fix update of ltrace and enhancement update of memstomp. For detailed information on changes in Red Hat Developer Toolset, see Red Hat Developer Toolset User Guide.
Red Hat Developer Toolset 3.1 introduces the devtoolset-3-dockerfiles subpackage for Red Hat Enterprise Linux 7. This package contains Dockerfiles for selected Red Hat Developer Toolset components, including their Red Hat Enterprise Linux 6 versions, which can be deployed only on Red Hat Enterprise Linux 7 Server. For details, see Red Hat Developer Toolset User Guide.

1.3.3. Changes in Perl

Perl 5.20.1, shipped in the new rh-perl520 Software Collection, introduces various changes and improvements, for example:
  • Hashes have been randomized by default; the order in which keys and values are returned from a hash now changes on each Perl run
  • Enabling locale now affects the character type
  • Support for Unicode 6.3 has been added
  • New hash slices have been added.

1.3.4. Changes in PHP

PHP 5.4

The php54 Software Collection has been upgraded to version 5.4.40, which provides a number of bug fixes over the version shipped in Red Hat Software Collections 1.

PHP 5.5

The updated php55 Software Collection includes PHP 5.5.21 with multiple bug fixes over the version shipped in Red Hat Software Collections 1.

PHP 5.6

The new rh-php56 Software Collection includes PHP 5.6.5 with PEAR 1.9.5 and the memcache, mongo, and XDebug extensions. This version provides a number of language and interface improvements. Refer to the upstream documentation on migration and the documentation for the PHP Interactive Debugger, which is provided by the rh-php56-php-dbg package.

1.3.5. Changes in Python

Python 2

The python27 Software Collection has been upgraded to version 2.7.8, which provides numerous security and bug fixes. This Software Collection now includes the python-wheel and python-pip modules.

Python 3

The new rh-python34 Software Collection includes Python 3.4.2, which provides numerous security fixes and several new features. Among others:
  • The pathlib module providing object-oriented file system path
  • Enumerated type (enum) is now part of the Python standard library (PEP 435)
  • Import-related standard library module changes
  • A new statistics module
  • The asyncio module, which enables writing code that concurrently handles asynchronous network based interactions.
This update also includes several changes to improve security, for example:
  • Certificates are now verified by default in the httplib module
  • TLSv1.1 and TLSv1.2 support for SSL has been added
  • Server-side Server Name Indication (SNI) support for SSL has been added.

1.3.6. Changes in Ruby

The new rh-ruby22 Software Collection contains Ruby 2.2.2, which provides substantial performance and reliability improvements, including:
  • A new incremental garbage collection (GC) algorithm has been included
  • Symbols are now garbage collectable
  • Minor improvements on the core classes and the standard library have been introduced.
Ruby 2.2 is backward compatible with Ruby 2.0.0 and Ruby 1.9.3. The ruby193 and ruby200 Software Collections are still available. For information about length of support for these components, refer to the Red Hat Software Collections Product Life Cycle document. Note that upstream development of Ruby 1.9.3 has been terminated and it is advisable to migrate to the rh-ruby22 Software Collection.

1.3.7. Changes in Ruby on Rails

Ruby on Rails 4.1.5, shipped in the new rh-ror41 Software Collection, provides the following major new features:
  • Spring Application Preloader to speed up development
  • The config/secrets.yml file, which can be used to store multiple secrets and access keys
  • Action Pack Variants to render different templates for phones, tablets, and browsers
  • Action Mailer Previews for email viewing
  • Active Record enums
  • Message Verifiers to generate and verify signed messages
  • A new Module#concerning to separate responsibilities within a class
  • Cross-site request forgery (CSRF) protection from remote <script> tags.
The rh-ror41 Software Collection is supported together with the rh-ruby22 Collection.

1.3.8. Changes in MariaDB

The new rh-mariadb100 Software Collection includes MariaDB 10.0.17, which provides a number of bug fixes, performance improvements, and enhancements over the version shipped in Red Hat Software Collections 1. The most notable changes are:
  • Parallel replication, which enables MariaDB to execute queries on the slave in parallel
  • Global transaction ID, which allows to easily change a slave server to connect to and a master server to replicate from; the state of the slave is recorded in a crash-safe way
  • Multi-source replication, which means that one server has multiple masters from which it replicates
  • New NoSQL features that add access to diverse data sources dynamically
  • New sharding features that allow database tables to be split across servers.
For more information regarding features in MariaDB 10.0, refer to the upstream resources. For information about migrating to the rh-mariadb100 Software Collection, see Section 5.1, “Migrating to MariaDB 10.0”.
For all practical purposes, MariaDB is a binary drop in replacement of the same MySQL version. For example, My SQL5.5 is compatible with MariaDB 5.5 and also in practice with MariaDB 10.0. For more information about MariaDB and MySQL compatibility, see the MariaDB documentation. Incompatibilities between MariaDB 10.0 and MySQL 5.6 are described in this section.

1.3.9. Changes in MongoDB

MongoDB 2.6.9, included in the new rh-mongodb26 Software Collection, provides a number of bug fixes and enhancements over the version shipped in Red Hat Software Collections 1. For example:
  • Aggregation enhancements — the aggregation pipeline adds the ability to return result sets of any size, either by returning a cursor or writing the output to a collection
  • Text search integration — text search is now enabled by default and the query system includes the $text operator, which resolves text-search queries
  • Improvements to the update and insert systems, which include additional operations and improvements that increase consistency of modified data
  • A new authorization model that provides the ability to create custom User-Defined Roles and the ability to specify user privileges at a collection-level granularity.
For detailed information on changes in MongoDB 2.6, refer to the MongoDB documentation. For information about migrating to the rh-mongodb26 Software Collection, see Section 5.2, “Migrating to MongoDB 2.6”.

1.3.10. Changes in MySQL

The new rh-mysql56 Software Collection includes MySQL 5.6.24, which provides a number of bug fixes, performance improvements, and enhancements over the version shipped in Red Hat Software Collections 1. Among others:
  • Parallel replication, which enables MySQL to execute queries on the slave in parallel
  • Global transaction ID, which allows to easily change a slave server to connect to and a master server to replicate from; the state of the slave is recorded in a crash-safe way
  • InnoDB memcached plug-in, which enables direct access to InnoDB tables using the memcached protocol and client libraries
  • New NoSQL-style memcached APIs
  • Optimizer improvements for all-around query performance
  • Partitioning improvements for querying and managing huge tables
  • Improved performance monitoring using the Performance Schema.
For more information about changes in MySQL 5.6, refer to the MySQL documentation. For information about migrating to the rh-mysql56 Software Collection, see Section 5.3, “Migrating to MySQL 5.6”.

1.3.11. Changes in PostgreSQL

PostgreSQL 9.4.1, provided by the new rh-postgresql94 Software Collection, includes the following most notable changes:
  • Increased flexibility with the new JSONB datatype, which enables users to use both relational and non-relational data stores at the same time
  • Increased scalability with Logical Decoding that supplies a new API for reading, filtering and manipulating the PostgreSQL replication stream. This interface is the foundation for new replication tools, such as Bi-Directional Replication.
  • Increased performance with improvements to GIN indexes, concurrently updatable Materialized Views for faster, more up-to-date reporting, parallel writing to the transaction log, and support for Linux huge pages.
  • Event trigger support for DDL
  • Improved materialized view, which can, for example, be refreshed without blocking concurrent reads
  • Updatable views
For detailed changes, see the PostgreSQL 9.3 Release Notes and the PostgreSQL 9.4 Release Notes. For information about migrating to the rh-postgresql94 Software Collection, see Section 5.4, “Migrating to PostgreSQL 9.4”.

1.3.12. Changes in Node.js

The nodejs010 Software Collection has been upgraded to upstream version 0.10.35, which provides a number of bug fixes and enhancements over the version shipped in Red Hat Software Collections 1. Among others:
  • Support for the SPDY protocol version 3.1 has been included for both Red Hat Enterprise Linux 6 and Red Hat Enterprise Linux 7
  • The nodejs010 Software Collection is now fully supported.

1.3.13. Changes in nginx

The nginx16 Software Collection has been upgraded to version 1.6.2, which provides several bug fixes and enhancements over the version shipped in Red Hat Software Collections 1. For example:
  • Support for Passenger has been added — see Section 4.7, “Passenger” for details
  • This update includes support for SPDY 3.1 for both Red Hat Enterprise Linux 6 and Red Hat Enterprise Linux 7.

1.3.14. Changes in Apache httpd

The httpd24 Software Collection has been upgraded to version 2.4.12, which provides numerous bug fixes and enhancements over the version shipped in Red Hat Software Collections 1. Among others:
  • Support for Passenger has been added — see Section 4.7, “Passenger” for details
  • Support for Elliptic curve Diffie–Hellman (ECDH) has been added
  • Support for Unix Domain Socket (UDS) in the mod_proxy_fcgi module has been improved
  • Installation of the mod_ssl module in FIPS mode has been fixed.

1.3.15. Changes in Thermostat

The thermostat1 Software Collection has been upgraded to version 1.2.0, which introduces several new features:
  • A new instrumenting profiler plug-in has been added
  • The setup of secured Thermostat using web storage has been simplified; the default setup has been changed to use HTTP-based storage
  • Various improvements have been introduced, for example, in the Swing client GUI and in a number of charts.
Note that data migration and automatic user plug-in migration is not supported from Thermostat 1.0.4 to Thermostat 1.2. For details, refer to the Thermostat documentation.

1.3.16. Changes in DevAssistant

The devassist09 Software Collection has been upgraded to version 0.9.3, which provides various bug fixes and several minor improvements, for example:
  • GitHub token is no longer logged for security reasons
  • Icons in the PNG format are supported in the DevAssistant GUI
  • Error messages can now be ignored when running commands in assistants.
For information about possible incompatibility with the previous version of DevAssistant, see Section 4.5.4, “Backward Compatibility in DevAssistant”.

1.4. Compatibility Information

Red Hat Software Collections 2.0 is available for all supported releases of Red Hat Enterprise Linux 6 and Red Hat Enterprise Linux 7 on AMD64 and Intel 64 architectures.

1.5. Known Issues

rh-mysql56, rh-mariadb100 components, BZ#1194611
The rh-mysql56-mysql-server and rh-mariadb100-mariadb-server packages no longer provide the test database by default. Although this database is not created during initialization, the grant tables are prefilled with the same values as when test was created by default. As a consequence, upon a later creation of the test or test_* databases, these databases have less restricted access rights than is default for new databases.
Additionally, when running benchmarks, the run-all-tests script no longer works out of the box with example parameters. You need to create a test database before running the tests and specify the database name in the --database parameter. If the parameter is not specified, test is taken by default but you need to make sure the test database exist.
httpd24 component, BZ#1224763
When using the mod_proxy_fcgi module with FastCGI Process Manager (PHP-FPM), httpd uses port 8000 for the FastCGI protocol by default instead of the correct port 9000. To work around this problem, specify the correct port explicitly in configuration.
rh-passanger40 component, BZ#1196555
When Passenger from the rh-passenger40 Software Collection is run as a module for httpd, the functionality is restricted by SELinux policy. To work around this problem, switch the passenger domain to permissive mode by running the following command as root: 
semanage permissive -a passenger_t
Standalone server and nginx integration are not affected by this issue.
mongodb24 component
The mongodb24 Software Collection from Red Hat Software Collections 1.2 cannot be rebuilt with the rh-java-common and maven30 Software Collections shipped with Red Hat Software Collections 2.0. Additionally, the mongodb24-build and mongodb24-scldevel packages cannot be installed with Red Hat Software Collections 2.0 due to unsatisfied requires on the maven30-javapackages-tools and maven30-maven-local packages. When the mongodb24-scldevel package is installed, broken dependencies are reported and the yum --skip-broken command skips too many packages. Users are advised to update to the rh-mongodb26 Software Collection.
perl component
When the user tries to use the mod_perl module from both the rh-perl520 and perl516 Software Collections, a conflict in the /opt/rh/httpd24/root/usr/lib64/httpd/modules/mod_perl.so file occurs. As a consequence, it is impossible to use mod_perl from more than one Perl Software Collection.
nodejs010 component
Shared libraries provided by the nodejs010 Software Collection, namely libcares, libhttp_parser, and libuv, are not properly prefixed with the Collection name. As a consequence, conflicts with the corresponding system libraries might occur.
nodejs-hawk component
The nodejs-hawk package uses an implementation of the SHA-1 and SHA-256 algorithms adopted from the CryptoJS project. In this release, the client-side JavaScript is obfuscated. The future fix will involve using crypto features directly from the CryptoJS library.
postgresql component
The rh-postgresql94 and postgresql92 packages for Red Hat Enterprise Linux 6 do not provide the sepgsql module as this feature requires installation of libselinux version 2.0.99, which is not available in Red Hat Enterprise Linux 6.
httpd, mariadb, mongodb, mysql, nodejs, perl, php55, rh-php56, python, ruby, ror, thermostat, and v8314 components, BZ#1072319
When uninstalling the httpd24, mariadb55, rh-mariadb100, mongodb24, rh-mongodb26, mysql55, rh-mysql56, nodejs010, perl516, rh-perl520, php55, rh-php56, python27, python33, rh-python34, ruby193, ruby200, rh-ruby22, ror40, rh-ror41, thermostat1, or v8314 packages, the order of uninstalling can be relevant due to ownership of dependent packages. As a consequence, some directories and files might not be removed properly and might remain on the system.
mariadb, mysql, postgresql, mongodb components
Red Hat Software Collections 2.0 contains the MySQL 5.6, MariaDB 10.0, PostgreSQL 9.4 and MongoDB 2.6 databases. The core Red Hat Enterprise Linux 6 provides earlier versions of the MySQL and PostgreSQL databases (client library and daemon). The core Red Hat Enterprise Linux 7 provides earlier versions of the MariaDB and PostgreSQL databases (client library and daemon). Client libraries are also used in database connectors for dynamic languages, libraries, and so on.
The client library packaged in the Red Hat Software Collections database packages in the PostgreSQL component is not supposed to be used, as it is included only for purposes of server utilities and the daemon. Users are instead expected to use the system library and the database connectors provided with the core system.
A protocol, which is used between the client library and the daemon, is stable across database versions, so, for example, using the PostgreSQL 9.2 client library with the PostgreSQL 9.4 daemon works as expected.
The core Red Hat Enterprise Linux 6 and Red Hat Enterprise Linux 7 do not include the client library for MongoDB. In order to use this client library for your application, you should use the client library from Red Hat Software Collections and always use the scl enable ... call every time you run an application linked against this MongoDB client library.
mariadb, mysql, mongodb components
MariaDB, MySQL, and MongoDB do not make use of the /opt/provider/collection/root prefix when creating log files. Note that log files are saved in the /var/opt/provider/collection/log/ directory, not in /opt/provider/collection/root/var/log/.
httpd component
Compiling external applications against the Apache Portable Runtime (APR) and APR-util libraries from the httpd24 Software Collection is not supported. The LD_LIBRARY_PATH is not set in httpd24 because it is not required by any application in this Software Collection.
httpd, ruby193 components, BZ#1071145
In Red Hat Enterprise Linux 6.5 and earlier versions, httpd is unable to execute the binary files in the mod_passenger module, namely PassengerWatchdog, PassengerHelperAgent, PassengerLoggingAgent, and SpawnPreparer in the /opt/rh/ruby193/root/usr/lib64/gems/exts/passenger-4.0.18/agents/ directory. To work around this problem, disable SELinux by running the following command as root: 
setenforce 0
nginx component, BZ#1045041
In Red Hat Enterprise Linux 6.5 and earlier versions, no SELinux policy is applied for the nginx daemon.
python27 component
In Red Hat Enterprise Linux 7, when the user tries to install the python27-python-debuginfo package, the /usr/src/debug/Python-2.7.5/Modules/socketmodule.c file conflicts with the corresponding file from the python-debuginfo package installed on the core system. Consequently, installation of the python27-python-debuginfo fails. To work around this problem, uninstall the python-debuginfo package and then install the python27-python-debuginfo package.
devassist component
When the user tries to rebuild the devassist09-PyYAML package on Red Hat Enterprise Linux 6, the build fails due to a soft dependency, if the Pyrex or Cython programming languages are detected. To work around this problem, make sure the pyrex or cython packages are not installed on your system.

Other Notes

rh-ruby22, rh-python34, rh-php56 components
Using Software Collections on a read-only NFS has several limitations.
  • Ruby gems cannot be installed while the rh-ruby22 Software Collection is on a read-only NFS. Consequently, for example, when the user tries to install the ab gem using the gem install ab command, the following error message is displayed: 
    ERROR:  While executing gem ... (Errno::EROFS)
    Read-only file system @ dir_s_mkdir - /opt/rh/rh-ruby22/root/usr/local/share/gems
    The same problem occurs when the user tries to update or install gems from an external source by running the bundle update or bundle install commands.
  • When installing Python packages on a read-only NFS using the Python Package Index (PyPI), running the pip command fails with an error message similar to this: 
    Read-only file system: '/opt/rh/rh-python34/root/usr/lib/python3.4/site-packages/ipython-3.1.0.dist-info'
  • Installing packages from PHP Extension and Application Repository (PEAR) on a read-only NFS using the pear command fails with the error message: 
    Cannot install, php_dir for channel "pear.php.net" is not writeable by the current user
This is an expected behavior.
thermostat component
Previously, it was sufficient to start the Thermostat storage and agent back ends by running the thermostat service command. With this update, it is necessary to first run the thermostat-setup command and then configure the agent manually with credentials in the agent.auth file. For details, refer to the Thermostat User Guide.
thermostat component
The thermostat1-thermostat-tomcat start command, which starts the Thermostat web storage endpoint, can be used only on Red Hat Enterprise Linux 6 and Red Hat Enterprise Linux 7.0. On Red Hat Enterprise Linux 7.1 and later versions, use service tomcat@thermostat start instead.
httpd component
Language modules for Apache are supported only with the Red Hat Software Collections version of Apache httpd and not with the Red Hat Enterprise Linux system versions of httpd. For example, the mod_wsgi module from the rh-python34 Collection can be used only with the httpd24 Collection.
all components
Since Red Hat Software Collections 2.0, configuration files, variable data, and runtime data of individual Collections are stored in different directories than in previous versions of Red Hat Software Collections.
coreutils component
Some utilities, for example, su, login, or screen, do not export environment settings in all cases, which can lead to unexpected results. It is therefore recommended to use sudo instead of su and set the env_keep environment variable in the /etc/sudoers file. Alternatively, you can run commands in a reverse order; for example: 
su -l postgres -c "scl enable rh-postgresql94 psql"
instead of 
scl enable rh-postgresql94 bash
su -l postgres -c psql
When using tools like screen or login, you can use the following command to preserve the environment settings: 
source /opt/rh/<collection_name>/enable
php54 component
Note that Alternative PHP Cache (APC) in Red Hat Software Collections is provided for user data cache only. For opcode cache, Zend OPcache is provided.
python component
When the user tries to install more than one scldevel package from the python27, python33, and rh-python34 Software Collections, a transaction check error message is returned. This is an expected behavior because the user can install only one set of the macro files provided by the packages (%scl_python, %scl_prefix_python).
php component
When the user tries to install more than one scldevel package from the php54, php55, and rh-php56 Software Collections, a transaction check error message is returned. This is an expected behavior because the user can install only one set of the macro files provided by the packages (%scl_php, %scl_prefix_php).
ruby component
When the user tries to install more than one scldevel package from the ruby193, ruby200, and rh-ruby22 Software Collections, a transaction check error message is returned. This is an expected behavior because the user can install only one set of the macro files provided by the packages (%scl_ruby, %scl_prefix_ruby).
perl component
When the user tries to install more than one scldevel package from the perl516 and rh-perl520 Software Collections, a transaction check error message is returned. This is an expected behavior because the user can install only one set of the macro files provided by the packages (%scl_perl, %scl_prefix_perl).
nodejs component
When installing the nodejs010 Software Collection, nodejs010 installs GCC in the base Red Hat Enterprise Linux system as a dependency, unless the gcc packages are already installed.