What's with the symlinks?

What's with the symlinks?

[Matthew Palmer]

Everywhere I go while assembling my OE build tree, I see admonishments not
to use a path that has symlinks in it.  For such a major problem, the only
real information on the actual problem is a fairly cryptic entry in the FAQ,
about a failure to build libtool-native.

Being an intensely curious kind of person, and not enjoying arbitrary
limits, I'm very interested to know what the *real* reason behind being so
strongly against the much-maligned symlink.  Can anyone enlighten me?

- Matt

-- 
English is about as pure as a cribhouse whore. We don't just borrow
words; on occasion, English has pursued other languages down alleyways
to beat them unconscious and rifle their pockets for new vocabulary."
	-- James D. Nicoll, resident of rec.arts.sf.written

Re: What's with the symlinks?

[Robert Wörle]

Dear Matthew

I cant answer your question but i can say ,, it works for me like a charm...

I have a partition where the whole oe stuff is residing ( tree , tmp`s
for various builds ) but i symlinked it inot my /home folder and also
use it in there
so i dont have any problem ( but i remmeber having problems at least a
year ago with symlinking the tree )

Maybe that faq is outdated and not "valid" anymore

Regards
rob_w

Matthew Palmer schrieb:
> Everywhere I go while assembling my OE build tree, I see admonishments not
> to use a path that has symlinks in it.  For such a major problem, the only
> real information on the actual problem is a fairly cryptic entry in the FAQ,
> about a failure to build libtool-native.
>
> Being an intensely curious kind of person, and not enjoying arbitrary
> limits, I'm very interested to know what the *real* reason behind being so
> strongly against the much-maligned symlink.  Can anyone enlighten me?
>
> - Matt
>
>   

Re: What's with the symlinks?

[jack-oe]

On Fri, Dec 29, 2006 at 11:11:29AM +1100, Matthew Palmer wrote:

> Everywhere I go while assembling my OE build tree, I see admonishments not
> to use a path that has symlinks in it.  For such a major problem, the only
> real information on the actual problem is a fairly cryptic entry in the FAQ,
> about a failure to build libtool-native.
 
> Being an intensely curious kind of person, and not enjoying arbitrary
> limits, I'm very interested to know what the *real* reason behind being so
> strongly against the much-maligned symlink.  Can anyone enlighten me?

I ran into this. IIRC if "$PWD" != "`readlink -f $PWD`", then automake-native
fails to build. 

This is a feature of the automake build system. 

--Jack 

--
Jack (John) Cummings                           http://mudshark.org/
PGP fingerprint: 0774 D073 E386 B70B 6B16  2D2B 1DD8 F8B0 CCF0 FAEE

Re: What's with the symlinks?

[Matthew Palmer]

On Thu, Dec 28, 2006 at 09:51:40PM -0800, jack-oe@mudshark.org wrote:
> On Fri, Dec 29, 2006 at 11:11:29AM +1100, Matthew Palmer wrote:
> 
> > Everywhere I go while assembling my OE build tree, I see admonishments not
> > to use a path that has symlinks in it.  For such a major problem, the only
> > real information on the actual problem is a fairly cryptic entry in the FAQ,
> > about a failure to build libtool-native.
>  
> > Being an intensely curious kind of person, and not enjoying arbitrary
> > limits, I'm very interested to know what the *real* reason behind being so
> > strongly against the much-maligned symlink.  Can anyone enlighten me?
> 
> I ran into this. IIRC if "$PWD" != "`readlink -f $PWD`", then automake-native
> fails to build. 
> 
> This is a feature of the automake build system. 

Interesting "feature".  I'd use a slightly different word for it, though.

- Matt

Re: What's with the symlinks?

[Koen Kooi]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

jack-oe@mudshark.org schreef:
> On Fri, Dec 29, 2006 at 11:11:29AM +1100, Matthew Palmer wrote:
> 
>> Everywhere I go while assembling my OE build tree, I see admonishments not
>> to use a path that has symlinks in it.  For such a major problem, the only
>> real information on the actual problem is a fairly cryptic entry in the FAQ,
>> about a failure to build libtool-native.
>  
>> Being an intensely curious kind of person, and not enjoying arbitrary
>> limits, I'm very interested to know what the *real* reason behind being so
>> strongly against the much-maligned symlink.  Can anyone enlighten me?
> 
> I ran into this. IIRC if "$PWD" != "`readlink -f $PWD`", then automake-native
> fails to build. 
> 
> This is a feature of the automake build system. 

It is a (wrong) check to see if builddir == sourcedir. With a symlink present, the
configure script thinks your building outside sourcedir and wants to create some files.
But those files are already present, so it fails with a "directory already configured"
message.

regards,

Koen
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Re: What's with the symlinks?

[Richard Purdie]

On Fri, 2006-12-29 at 11:11 +1100, Matthew Palmer wrote:
> Everywhere I go while assembling my OE build tree, I see admonishments not
> to use a path that has symlinks in it.  For such a major problem, the only
> real information on the actual problem is a fairly cryptic entry in the FAQ,
> about a failure to build libtool-native.
> 
> Being an intensely curious kind of person, and not enjoying arbitrary
> limits, I'm very interested to know what the *real* reason behind being so
> strongly against the much-maligned symlink.  Can anyone enlighten me?

People have explained the reason but you can use paths with symlinks in
*if* you're careful. Basically, you need to ensure the environmental
variables you set use absolute paths without symlinks. My scripts for
setting up build environments make suitable use of "basedir" to ensure
that.

Also, you need to have the conf and tmp directories in the directory
without any symlinks so tmp cannot be a symlink. I'm not entirely sure
why that breaks things but it does.

We should probably patch bitbake to avoid these issues. Patches welcome!

Richard

Re: What's with the symlinks?

[Jamie Lenehan]

On Fri, Dec 29, 2006 at 12:12:03PM +0000, Richard Purdie wrote:
> On Fri, 2006-12-29 at 11:11 +1100, Matthew Palmer wrote:
> > Everywhere I go while assembling my OE build tree, I see admonishments not
> > to use a path that has symlinks in it.  For such a major problem, the only
> > real information on the actual problem is a fairly cryptic entry in the FAQ,
> > about a failure to build libtool-native.
> > 
> > Being an intensely curious kind of person, and not enjoying arbitrary
> > limits, I'm very interested to know what the *real* reason behind being so
> > strongly against the much-maligned symlink.  Can anyone enlighten me?
> 
> People have explained the reason but you can use paths with symlinks in
> *if* you're careful. Basically, you need to ensure the environmental

It's also possible to use bind mounts, which lets you mount one
subdirectory over another subdirectory, to achieve a similiar sort of
effect. I have my oe stuff in ~/devel/oe which is a bind mount from a
seperate disk:

  [nynaeve][ 2:02PM]~/devel/oe%> df -h .
  Filesystem            Size  Used Avail Use% Mounted on
  /u/5QF1E359/oe        294G   69G  226G  24% /home/lenehan/devel/oe
  [nynaeve][ 2:02PM]~/devel/oe%> cat /etc/fstab | grep oe
  /u/5QF1E359/oe          /home/lenehan/devel/oe  none    bind            0 0
  [nynaeve][ 2:04PM]~/devel/oe%> mount | grep 5QF1E359
  /dev/sdc2 on /u/5QF1E359 type ext3 (rw)
  /u/5QF1E359/oe on /home/lenehan/devel/oe type none (rw,bind)

So instead of a symlink from ~/devel/oe to /u/5QF1E359/oe I mounted (via a
bind mount) /u/5QF1E359/oe on ~/devel/oe

-- 
 Jamie Lenehan <lenehan@twibble.org>