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Re: /usr/lib vs /usr/libexec

On Tuesday 10 May 2005 02:18, Goswin von Brederlow 
<brederlo@informatik.uni-tuebingen.de> wrote:
> Russell Coker <russell@coker.com.au> writes:
> > It seems to me that /usr/libexec is a better name for such things, and
> > having the same directory names used across distributions provides real
> > benefits (copying config files and binaries from other distributions when
> > a bug stops a server working and it's REALLY important to get it fixed
> > fast).
> >
> > Should we change some of these to /usr/libexec?
> That would be /usr/libexec/arch-os/postfix vs /usr/lib/arch-os/postfix
> then.
> If you consider any change then please include the multiarch changes
> at the same time. No point doing 2 transitions for etch.

Why would it be desirable to have arch-os directories under libexec?

By definition anything in libexec is a program that is a part of another 
program.  In the case of Postfix there are many cooperating programs running 
with different privs (different UID and different SE Linux domain) that are 
used for different aspects of Postfix functionality.  Why would you want one 
of those programs to be 32bit and another to be 64bit?

Firstly there is little performance to be gained by running Postfix 64bit.  
Any performance issues that a Postfix server will experience will be related 
to disk IO (not a word size issue) or the speed of external programs such as 
virus scanners and Postgrey (which interoperate with Postfix via TCP sockets 
and have no inter-dependencies on word size etc).

Secondly there is no benefit to using different word sizes for different parts 
of Postfix.  I can't imagine any reason for using different word sizes.  
There is a possibility of having Postfix call external shared objects which 
may make some dependencies on word size.  But if you have two shared objects 
one of which is 32bit and another 64bit then trying to get Postfix processes 
to use both will be a losing game.  AFAIK there is no design documentation 
which precisely states which Postfix sub-process will use a given shared 

Finally no-one has tested Postfix for such things.  I think that Postfix is 
very well written and should work even if you had parts of it being 64bit and 
parts being 32bit.  But this is not tested or guaranteed.  If there was a bug 
in this regard then it could have security implications, do you want to take 
the chance?

http://www.coker.com.au/selinux/   My NSA Security Enhanced Linux packages
http://www.coker.com.au/bonnie++/  Bonnie++ hard drive benchmark
http://www.coker.com.au/postal/    Postal SMTP/POP benchmark
http://www.coker.com.au/~russell/  My home page

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