PATH=/usr/local/bin:/bin:/usr/bin considered harmful

[John Ellson]

 > Having thought about it, I don't think it's unreasonable to do a 
"which $PROG", and stick it into the hashbang. I think that's a 
perfectly reasonable approach, with portability being the goal. The 
problem I see here, is > that Fedora's bash is compiled with the default 
PATH placing a symlink, /bin, ahead of /usr/bin, in the PATH list:

+1 on this.

This has very little to do with yum; It affects other programs too.    
It breaks graphviz builds, for example, because
its build scripts try to deduce various tcl paths from `which tclsh`

It is also a significant performance hit for every executable lookup to 
traverse an extra softlink from /bin -> /usr/bin.
Since there is nothing in /bin now, /bin should be after /usr/bin in the 
default PATH..

John




On 06/21/2012 11:15 PM, Sam Varshavchik wrote:
> The perl update that hit updates this week is causing a yum conflict 
> with some locally-built packages, of this type:
>
> Error: Package: courier-imap-4.10.0.20120202-2.17.x86_64 (installed)
>           Requires: /bin/perl
>           Removing: 4:perl-5.14.2-211.fc17.x86_64 (@anaconda-0)
>               Not found
>           Updated By: 4:perl-5.14.2-212.fc17.x86_64 
> (updates-released-local)
>               Not found
>
>> From what I can tell, the sequence of events is:
>
> A) A local package's configure script executes "which perl", and puts 
> that into each perl script's hashbang. So:
>
> [root at octopus ~]# which perl
> /bin/perl
>
> This results in:
>
> #! /bin/perl
>
> B) The rpm package gets built. find-requires that puts this dependency 
> into the package:
>
> requires=/bin/perl
>
> C) At install time, rpm seems to be smart to figure this out:
>
> [root at octopus ~]# rpm -q --whatprovides /bin/perl
> perl-5.14.2-211.fc17.x86_64
>
> It's smart enough sees that thanks to the symlinks, 
> /bin/perl=/usr/bin/perl. So the package gets installed, with these 
> hashbangs.
>
> D) A perl update hits:
>
> [root at shorty x86_64]# rpm -q -l -p perl-5.14.2-212.fc17.x86_64.rpm | 
> fgrep bin/perl
> /usr/bin/perl
> /usr/bin/perl5.14.2
> /usr/bin/perlbug
> /usr/bin/perlthanks
>
> The new perl package contains /usr/bin/perl. At upgrade, dependency 
> resolution is not smart enough to realize that the new package's 
> /bin/perl=/usr/bin/perl, causing a conflict.
>
> Having thought about it, I don't think it's unreasonable to do a 
> "which $PROG", and stick it into the hashbang. I think that's a 
> perfectly reasonable approach, with portability being the goal. The 
> problem I see here, is that Fedora's bash is compiled with the default 
> PATH placing a symlink, /bin, ahead of /usr/bin, in the PATH list:
>
> [root at octopus ~]# strings /bin/bash | grep usr.bin
> /usr/local/bin:/bin:/usr/bin
>
> I think that bash needs to be recompiled, with the last two flipped, 
> in the default shell PATH.
>
> Until then, I need to hack each one of my locally-built package's rpm 
> spec scripts, and manually prepend /usr/bin to the PATH. Which sucks.
>
>
>
>