[svlug] ubuntu 14.04 where are the wifi tables stored?

Rick Moen rick at svlug.org
Mon Jan 19 11:53:55 PST 2015


Scott DuBois wrote:

> You're going places now that I've never been so I have an 'idea' of what
> I'm looking at but I'm not seeing the dependencies that should be there.

Yeah, you know, having slept on it, I realise that I made an assumption in
recommending that you verify that the main vlc binary includes those
explicit library dependencies:  I assumed that VLC calls those three libs
directly as SO (shared object) files.  I actually don't know VLC all that
well.  If you (or someone else on this mailing list) happen to have an
installed copy of VLC on a different Linux distro where support for
encrypted Blu-Rays is known to be working, you could compare ldd output and
see if my assumption is true.

As to what you were looking at, well, you know what a library (SO-file) is
basically, right?  It's a binary routine that can be used by an executable
program.  When you compile a program from source, the author usually
specifies one or more libs it uses.  Compilation options choose whether to 
compile _statically_ (to incorporate the library bodily into the executable)
or _dynamically_, in which case a system facility called the dynamic linker 
searches its library paths (text lines on /etc/ld.so.conf by default) to
find the library files with the specified SOnames.

'ldd' shows the latter process for a dynamically linked executable.  As the 
man page says:  'ldd prints the shared libraries required by each program
or shared library specified on the command line.'

dash is a small Bourne-compatible shell.

$ ldd /bin/dash
	linux-gate.so.1 =>  (0xf57fe000)
	libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0xb7628000)
	/lib/ld-linux.so.2 (0xb77da000)
$ 


In that output, please ignore the 'linux-gate' line for now.  It's not a
real library, and it would take a while to explain what it is.  (Briefly,
it's an interface exposed by the kernel as the mechanism for making system
calls.  More at:  http://www.trilithium.com/johan/2005/08/linux-gate/ )
Likewise, ld-linux is a special entry for the dynamic linker itself.

Which leaves this line:

        libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0xb7628000)

The left side, 'libc.so.6' , is the SOname.  ldd is telling you that dash at
runtime indicates that it needs a library with shared object name libc.so.6'.  
Within that SOname, 'so' is of course just a naming convention to indicate
that this is a shared object, i.e., library.  'libc' is the actual name of
the library in question.  '6' is the _major_ library number.  There can also
be a minor library number for small changes, not used here.

'/lib/i386-linux-gnu/libc.so.6' is the specific on-disk file that the system
dynamic linker found with the required SOname.  This is what the executable
will use at runtime for its 'libc' functions.

'0xb7628000' is the load address in memory of that library.  See:
http://stackoverflow.com/questions/5130654/when-how-does-linux-load-shared-libraries-into-address-space/5130690#5130690
And, if that's not detailed enough:
http://www.akkadia.org/drepper/dsohowto.pdf


> I also went back and looked at that link you sent me. I may have passed on
> those instructions since they included a ppa. Yeah, just checked, not in
> my repo list.  Maybe I should just consider doing that?

{shrug}  Not sure offhand how you use a PPA archive ona Debian system
However, at worst, you could just pull down the files and open them
manually.  A deb file is just an 'ar' archive (just as an rpm is just a cpio
archive).

> Yes, I hardly ever use CD/DVD medium much anymore other than for boot
> disks and watching movies.

Just in case my point was unclear:  When you are having problems with
_encrypted_ Blu-Rays, not with any old Blu-Ray in its capacity as a nice,
large-capacity optical mass-storage device, it's in your interest to use
wording that makes it clear your problem's the one thing rather than the
other.

You said you couldn't read Blu-Rays on your Debian Stable installation.  
Making any Linux distribution able to read and write Blu-Rays is easy, e.g.,
you can burn them using growisofs (http://linux.die.net/man/1/growisofs) and
mount them using the UDF filesystem.

Someone less wary might have answered you by pointing you to that
information.  However, 'I would love to be able to watch my blu-rays on
Debian' was not exactly what you meant.  It was only what you _said_,
because it probably never occurred to you that all Blu-Rays are not alike,
and that you really meant 'I would love to be able to watch my _encrypted_
Blu-Rays [or studio-movie Blu-Rays] on Debian.'

The point is, those are different problems.






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