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List:       klik-devel
Subject:    Re: [klik-devel] strace question
From:       RazZziel <razielmine () gmail ! com>
Date:       2008-01-21 7:30:37
Message-ID: 82e274890801202330u28a59d27v4d8a649150e410eb () mail ! gmail ! com
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Hi there,

I have no idea about the specific fuseiso code, but in general terms,
hope this helps:
http://ask.slashdot.org/article.pl?sid=08/01/18/1554257

Ismael

On Jan 21, 2008 9:05 AM, Ng, Cheon-woei <cheon-woei.ng@intel.com> wrote:
> Hi Lionel,
> 
> Thank you for your excellent explanations!  I wish to understand how fuseios and \
> fakechroot works in the source code level by following the code paths, but without \
> doing too many grep.  May be using cscope or doxygen would help?  Do you have any \
> other suggestions?  Thanks! 
> Sincerely,
> Cheon-Woei Ng
> 
> 
> 
> -----Original Message-----
> From: Lionel Tricon [mailto:lionel.tricon@free.fr]
> Sent: Sunday, January 20, 2008 9:17 AM
> To: Ng, Cheon-woei
> Cc: klik-devel@kde.org
> Subject: Re: [klik-devel] strace question
> 
> 
> Hello,
> 
> Well, it depends of what you want to understand about klik2.
> 
> You need to evaluate separately the klik2 python base code (the build and gui
> part) and all the stuff behind (fuseiso, fakechroot), the backend (run) part.
> 
> The main idea is to union the real root fs and all files located into an
> iso 'cmg' file into a single mount point (thanks to a patched fuseiso
> utility).
> 
> Fakechroot is used mainly to put the previous mount point under a jail to give
> the illusion for the program we want to execute that it runs under the real
> root fs (which is not true). Since special files and /proc are not emulated
> by fuse (for some security reasons), we have hacked fakechroot (based on
> LD-PRELOAD) to give direct access to a list of directory (/proc, /dev, ...).
> 
> If you strace kwrite, for example, under klik and the shell mode, you should
> got the following :
> 
> lstat64("/tmp/klik/bDEm_j.execute.xvier_1.0-7.3.cmg/home/lionel",
> {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
> chdir("/tmp/klik/bDEm_j.execute.xvier_1.0-7.3.cmg/") = 0
> access("/tmp/klik/bDEm_j.execute.xvier_1.0-7.3.cmg/home/lionel/.kde/share/config/kwriterc",
>  W_OK) = 0
> open("/tmp/klik/bDEm_j.execute.xvier_1.0-7.3.cmg/home/lionel/.kde/share/config/kwriterc.lock34ee8a.tmp",
>  O_RDWR|O_CREAT|O_EXCL, 0600) = 13
> 
> It appears that instead of reading files/directories from the real fs
> (/home/lionel), fakechroot overload all path with the union path
> (currently, /tmp/klik/bDEm_j.execute.xvier_1.0-7.3.cmg) to
> give /tmp/klik/bDEm_j.execute.xvier_1.0-7.3.cmg/home/lionel.
> 
> Hope that what you were looking for. Don't hesitate to play with fuseiso and
> fakechroot to learn more about all klik technologies.
> 
> For example :
> $ mkdir -p /tmp/app/1
> $ export PATH=/opt/klik/bin:$PATH
> $ /opt/klik/bin/fuseiso -n -u /home/lionel/Desktop/xvier_1.0-7.3.cmg /tmp/app/1/
> $ export LD_LIBRARY_PATH=/opt/klik/lib:$LD_LIBRARY_PATH
> $ export FAKECHROOT_BASE=/tmp/app/1
> $ export LD_PRELOAD=libfakechroot.so
> $ cat /recipe.xml
> 
> Here, you should obtain the content of the recipe.xml file located at the root
> of the iso file.
> 
> If you unset the LD_PRELOAD env var :
> lionel@kubuntu:~$ unset LD_PRELOAD
> lionel@kubuntu:~$ cat /recipe.xml
> cat: /recipe.xml: Aucun fichier ou répertoire de ce type
> 
> To unmount it :
> $ unset LD_PRELOAD
> $ /opt/klik/bin/fusermount -u /tmp/app/1
> 
> The python code is 'only' a graphical frontend to all of these commands :-)
> But a very nice frontend indeed !!!
> 
> Lionel
> 
> On Saturday 12 January 2008 01:37:57 Ng, Cheon-woei wrote:
> > Hi Kurt,
> > 
> > Thank you.  I am not sure if this if what I am looking for.  I want to
> > understand how klik works in the source code level, like
> > 
> > Klik path_to_cmg would call klik.execute_cmg
> > Klik.execute_cmg would in turn calls klikExecute(self), then ex.execute
> > Ex.execute would calls self.__prep
> > __prep would call self.mount_cmg
> > So on and so forth.
> > 
> > Other than reading the source code line by line, is there any good/more
> > efficient way (other than using strace) to understand code path?
> > 
> > Thanks again! Have a great weekend!
> > 
> > Sincerely,
> > Woei
> _______________________________________________
> klik-devel mailing list
> klik-devel@kde.org
> https://mail.kde.org/mailman/listinfo/klik-devel
> 



-- 
...yet even then, we ran like the wind, whilst our laughter echoed,
under cerulean skies...
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