2007-02-14
RPM tricks for dealing with multiarch machines
Why do we need some new RPM tricks for dealing with multiarch machines? Simple:
; rpm -q glibc glibc-2.5-10.fc6 glibc-2.5-10.fc6
That's not an error, that's just my machine having both the 32-bit and
the 64-bit glibc RPMs installed. On a multiarch machine it's routine
to have RPMs with identical names, and rpm itself hasn't been fully
adapted for this situation.
The big RPM trick for dealing with a multiarch machine is to know that you can pick out a specific architecture's RPM by putting the name of the architecture on the end of the name of the RPM:
; rpm -q glibc.x86_64 glibc-2.5-10.fc6
(You can use this format with yum as well as with rpm.)
The other trick is using RPM query formats to actually show you which architecture a specific RPM is for. Query formats are sufficiently complicated that a full explanation is well beyond the scope of this entry, but the basics are reasonably simple:
; rpm --qf '%{NAME}.%{ARCH}\n' -q glibc
glibc.x86_64
glibc.i686
The normal 'rpm -q' output format is
'%{NAME}-%{VERSION}-%{RELEASE}\n', or '%{N}-%{V}-%{R}\n' in the compact
form (technically this is slightly incorrect because it omits the
epoch, but that almost never matters). To add the architecture you use
an explicit query format of '%{N}-%{V}-%{R}.%{ARCH}\n', and for many
purposes just the name and the architecture is enough, so you can just
use '%{NAME}.%{ARCH}\n'.
(And the '\n' is important. Many a time I've accidentally left it out and gotten all of the output smashed together into one line.)
There is probably something you can set up in your .rpmmacros file
to make rpm use this query format by default, but I don't know it.
You can just make a cover script instead, so you don't have to type the
query format all the time:
; cat rpmq
#!/bin/sh
exec rpm --qf '%{N}-%{V}-%{R}.%{ARCH}\n' "$@"
(My fingers are busy telling me that this should also supply the '-q'
argument too, so I can just do 'rpmq kernel' and it'll work.)