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Bug#447609: ldconfig triggerisation



On Mon, Oct 22, 2007 at 04:07:05PM +0100, Ian Jackson wrote:
> The understanding on which we base this approach is that after library
> installation (which is when ldconfig is used in maintainer scripts) it
> is always safe to defer the execution of ldconfig.  Ie, that after a
> new library has been installed or an existing library upgraded,
> programs which link against the library will work even though ldconfig
> hasn't been run.  We understand that not running ldconfig will incur
> some performance penalty during the upgrade process but in practice
> this is far outweighed by the cost of repeatedly running ldconfig.

Note that this is usually true but not always; it may be true
enough for our purposes but I want to set the record straight.

ld.so searches LD_LIBRARY_PATH plus /usr/lib and /lib, and standard
hwcap subdirectories of those.  It does not read /etc/ld.so.conf, nor
does it search the "tls" subdirectories still used in some places to
find NPTL.

The only failure case I can think of would be a package which places
libraries in the multi-arch directories, which Debian locates using a
file in /etc/ld.so.conf.d, and the same or another package which runs
a newly installed program using the library from the first package
in its postinst.

If usage of those directories is planned to increase this may become
a problem.

-- 
Daniel Jacobowitz
CodeSourcery




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