Anyone running centos/rhel x86_64 systems has probably noticed that redhat has a strange way to install a mix of i386 and x86_64 rpms on such a systems. This is how redhat is using the 64bit architecture in a mixed way to be able to support also i386 applications. This is completely different from how for example debian does this where you will not see by default any i386 libraries or duplicate applications installed (you can install and use ia32 libraries for compatibility reasons but the user is in full control on this process). The way how this works in rhel is confusing; let’s take a simple example (the commands are taken from a clean centos5.3 install with the base packages selected): let’s see what version of ncurses we have on the system:
rpm -qa | grep ncurses
ncurses-5.5-24.20060715
ncurses-5.5-24.20060715
what? why is this listed twice? hmm… Running: rpm -qi ncurses-5.5-24.20060715 will also list the package twice (but doesn’t show the difference). We can assume one is i386 and one is x86_64 right? but we can’t see this.
To overcome this issue, and at least have rpm report the proper versions we have to add in our rpmmacros file a new line like: “%_query_all_fmt %%{name}-%%{version}-%%{release}.%%{arch}” that will add to the rpm output the architecture and allow us to see the this:
cat >> ~/.rpmmacros
%_query_all_fmt %%{name}-%%{version}-%%{release}.%%{arch}
and now running the same command will return a more intuitive and meaningful:
rpm -qa | grep ncurses
ncurses-5.5-24.20060715.x86_64
ncurses-5.5-24.20060715.i386
This doesn’t fix anything in how yum will install duplicate programs or libraries, but at least it will allow us to see the full name of the packages in rpm commands. Theoretically people should be able to add into yum.conf (this is the default anyway, so you might have it already):
exactarch=1
and yum will install by default the packages of the arch it is running on (x86_64 in our case). Still, this will not prevent i386 dependencies to show up and be installed. In case you want to completely ignore other arch packages add in the [main] section of /etc/yum.conf to exclude all 32bit packages,:
exclude=*.i386 *.i586 *.i686
and this will completely exclude them completely from yum operations. Please use this with care, and only if you have a full understanding of the implications to exclude those packages.
Even if you don’t exclude the 32bit packages as shown above, it is a good idea to add the arch to all yum operations (like install, remove, etc.), like:
yum install ncurses.x86_64
Hopefully you found this post useful, and have now a better understanding on how rhel/centos use the i368 and x86_64 packages and libraries with rpm and yum on a 64bit installation.
