Printing with Acrobat Reader

Rick C. Petty rick-freebsd at
Thu Apr 12 15:51:05 UTC 2007

[cc: line snipped]

On Thu, Apr 12, 2007 at 04:28:37PM +0200, Oliver Fromme wrote:
> Alexander Leidinger wrote:
>  > Oliver Fromme wrote:
>  > > That's correct.  Obviously Adobe Reader performs some kind
>  > > of sanity check on the path (if one is given), and for some
>  > > reason it always prepends /compat/linux in that case.
>  > 
>  > No linux application does this, it's the kernel. It tries with the  
>  > compat path first and then with the normal path. I don't know why it  
>  > does not work in acroread, I never investigated this issue. An  
>  > application should not be able to know if the command is from compat  
>  > or not.
> Adobe Reader does.  Dont ask me how and why, but it does.
> Any other explanation of the symptom is even less likely.

I get the sense that Acroread does something like the following:

opendir("/usr/bin")  --> maps to /compat because /usr/bin exists there
	readdir()	--> still reading from /compat/linux/usr/bin
"lpr" not found in /usr/bin/

I don't think our ABI layer checks for this kind of behavior.  Because
/compat/linux/usr/bin was found, it doesn't try to look in /usr/bin.  I've
seen this behavior in Acroread since version 7 and maybe even earlier, in
6-STABLE so it's not due to recent linux ABI changes.

Similarly, I've seen this behavior in linux-firefox.  Sometimes after
running ffox I'll notice that this directory gets completely filled:
and sometimes it doesn't.  I end up doing "rm -rf /compat/linux/home" a
lot and trying to restart ffox until it works from /home/$user.  My guess
is that the program picks up my profile in /home and reads most of the
files, but then tries to do a "mkdir -p" equivalent on /home/$user/...
but it's picking up in /compat somehow.

The ABI is performing similar to a unionfs but not quite, and maybe that's
the problem-- I think we want all writes to happen to the underlying
filesystem and all reads to check /compat first, but that may not be
trivial to implement at the VFS layer?  I think I even tried using symlinks
from /compat/linux/home to /home but the linux program sees:
/home --> /home

-- Rick C. Petty

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