A DRAFT statement on our build systems for Samba 4.0

[Andrew Bartlett]

On Thu, 2012-05-17 at 10:44 +1000, Andrew Bartlett wrote:
> I wanted to start a discussion about how we position and use the two
> build systems, so that when we get to a Samba 4.0 release, our users are
> clear on what build system provides what features, and why they should
> use it.  
> 
> I'm trying to make it clear in our user's minds that we have moved past
> having a 'file server' build and an 'AD build', and that for almost all
> users, the top level build is the one they want.
> 
> I fully expect that some of you will not agree with this DRAFT statement
> in whole, but then your constructive feedback is important:  If we do
> not have a common position, or we have technical issues that conflict
> with this statement, then we need to sort that out.  I want us all to
> understand the issues and (if technical) fix them, or (if philosophical)
> see if we can come up with something that we all agree on, so that when
> users of Samba 4.0 ask, they get a consistent answer. 
> 
> I would appreciate your thoughtful feedback and comments on this.

It was great to get a positive response from Alexander Bokovoy on IRC
this afternoon.  I've included below some small changes, and an extra
section addressing a question he had around optional libraries, ACLs in
particular.


> Samba 4.0 ships with a new build system, based on waf.  A background to
> this build system can be found at https://wiki.samba.org/index.php/Waf
> 
> This is the build system that is used when you run ./configure && make
> in the top level of a Samba 4.0 release tree.
> 
> For the vast majority of our users, this is the build system you should
> use.  It supports parallel and incremental builds, and builds the whole
> Samba suite, the file server, the print server, the NT4 domain
> controller, winbind, the AD Domain Controller, the client libraries and
> the python libraries.  
> 
> A key feature for many of our distributors and OEMs is that despite the
> range of additional features, the resulting binaries and libraries are
> substantially smaller, because we use shared libraries extensively. 
> 
> For distributions that have a requirement to use the system-supplied
> Kerberos library, by the time of the first release candidate, we will
> support building against a Heimdal or system MIT Kerberos library,
> provided the version is recent enough (otherwise we will use our
> internal version of Heimdal).  Please note that builds with MIT krb5
> support will not have AD DC features.
> 
> Also by the time of the first release candidate, we will finish renaming
> the binaries that we ship so that where we provide a tool under a name
> that was used in Samba 3.x, it continues to behave in the same way it
> always has.  This will ensure that our change in build system does not
> impact on our user's ability to use Samba as they always have.
> 
> For developers, this build system backs a comprehensive 'make test',
> which provides code coverage of around 48% of our code by line:
> https://build.samba.org/lcov/data/coverage/samba_4_0_test/
> 
> This build system also implements important features such as ABI
> checking (which protects you as users from accidental changes to our
> published libraries), symbol versions and dependency checked incremental
> rebuilds after header-file changes. 

The waf build also assists developers by providing fully-linked binaries
that run from bin/ without needing to set LD_LIBRARY_PATH. 

> For users who do not have python installed on their systems, we provide
> a install_with_python.sh script, which will install a local copy of
> python sufficient to run the build system, without impacting on the rest
> of the system.  
> 
> Within this requirement, we expect that this build will run on all our
> supported platforms, and will actively deal with any portability issues
> that users can bring to our attention. 
> 
> For all these reasons, we highly recommend this new build system to all
> our users, for whatever purpose you want to put Samba to.

The autoconf build
------------------

> For a small number of users, the requirement to have access to Python
> 2.4 and perl will be unacceptable, and for these users we continue to
> provide the 'autoconf' build system used in Samba 3.x under the
> source3/.  This will build less parts of Samba, but should not be seen
> as 'the file server build' (typical file server deployments should use
> the top level build), but as a measure provided with limited features
> for systems and organisations unable to meet the requirements for the
> new build system.
> 
> If you do need to use the autoconf build system, please let us know:
> both why you cannot use the 'waf' build in the top level, and what
> features of the source3 build that you require.  We need this
> information to assess the continuing demand for this parallel
> infrastructure, and to determine which features need to remain available
> in both build systems.

Optional Libraries
------------------

To assist users and distributors to build Samba with the full feature
set, the build system will abort if our dependent libraries and their
header files are not found on the target system.  This will mean for
example, that xattr, acl and ldap headers must be installed for the
default build to complete.  The configure system will check for these
headers, and the error message will indicate:
 - the required header and library
 - the option (such as --without-acl-support) that can be specified to
skip this requirement, and
 - the feature (ACL support optional for file servers, mandatory for AD
Domain Controller) being skipped. 

This will assist users and in particular distributors in building fully
functional packages, while allowing those on systems truly without these
facilities to continue to build Samba after careful consideration. 

> Again, this is a DRAFT.  I expect there are a wide range of views both
> on the team and from our user community.  I welcome that feedback, so we
> can be on as much of the same page as possible on this important issue
> when we make the 4.0 release.
> 
> Thanks,
> 
> Andrew Bartlett
> 

-- 
Andrew Bartlett                                http://samba.org/~abartlet/
Authentication Developer, Samba Team           http://samba.org