[TriLUG] Advanced RPM Dependencies

[Benjamin Reed]

Just had a conversation pop up about this in something unrelated to 
TriLUG, and I thought I'd pass it on to the list, since most of the 
knowlege on advanced RPM stuff is squirreled away in the depths of 
google, spread about in spec files (undocumented, of course), or stuck 
in the heads of folks at RedHat...  :)

We had run into problems with dependency-ordering at Oculan because our 
RPMs for our internal software are all fairly interdependent, and order 
of installation matters.  Unfortunately, if you're just using Requires 
and BuildRequires, you end up with pre running, all the files unpacking, 
and post running, in indeterminate order based on how RPM happens to 
hash things (as I understand it).

RPM4 has support for a whole lot of interesting ways to depend on 
things, at all stages of the build and install process.  Maximum RPM 
(and even most of the other documentation on rpm.org) misses a lot of 
this because it's fairly new and undocumented.

Basically, you can now add tokens to the Requires and BuildRequires 
fields to specify what part of the process they are required for, eg.:

   Requires(pre): foobar

...means that foobar needs to be installed *before* the preinstall of 
this package is run.  So if you're doing "rpm -U <package> foobar" it 
will still do the right thing...

Here are the tokens, and a general idea of what they mean as far as I 
can tell.  RedHat guys, if you know the specifics of the ones I'm 
unclear on, please let me know...

---(chomp)---
# For completeness, here's the complete set of tokens that may be
# added to Requires: as in the example above:
#
# "interp",             RPMSENSE_INTERP
# "prereq",             RPMSENSE_PREREQ
# "preun",              RPMSENSE_SCRIPT_PREUN
# "pre",                RPMSENSE_SCRIPT_PRE
# "postun",             RPMSENSE_SCRIPT_POSTUN
# "post",               RPMSENSE_SCRIPT_POST
# "rpmlib",             RPMSENSE_RPMLIB
# "verify",             RPMSENSE_SCRIPT_VERIFY
#
# Ditto BuildRequires:
# "prep",               RPMSENSE_SCRIPT_PREP
# "build",              RPMSENSE_SCRIPT_BUILD
# "install",            RPMSENSE_SCRIPT_INSTALL
# "clean",              RPMSENSE_SCRIPT_CLEAN
---(chomp)---

I *believe* this means:

interp:		interpretation time, ie, before it
		calls the shell for any of the
		subsections or macros (so if you have
		a bit that uses "python2.2" in setting
		up variables, it'll work)

prereq:		prerequisite of installing the package,
		this is a dependency before any files
		are unpackaged, or any pre/post-install
		scripts are run

pre:		dependency for the pre-install script

postun:		needed for the post-uninstall script

post:		needed for the post-install script

rpmlib:		not sure what this means...

verify:		needed for 'rpm verify' (you can override
		what 'rpm verify' does in the spec file
		if you want to do your own consistency
		checking... this token means your custom
		verify needs something)

And then the BuildRequires ones correspond to one of the %sections of 
the spec file.

...so then what I did was this:

---(chomp)---
# minimum versions
%define minimum_dbd_pg          1.13
%define minimum_dbi             1.30
%define minimum_healthcheck     3.2.99
%define minimum_j2sdk           1.4
%define minimum_opennms         %{onms_version}-%{o_release}
%define minimum_postgresql      7.1.3-0.onms.5
%define minimum_rrdtool         1.0.37-0.oculan.7
%define minimum_tomcat4         4.1.18-full

# postgresql
BuildRequires(build):   postgresql        >= %{minimum_postgresql}
BuildRequires(build):   postgresql-server >= %{minimum_postgresql}
BuildRequires(build):   postgresql-devel  >= %{minimum_postgresql}
BuildRequires(build):   compat-libstdc++
Requires(prereq):       postgresql        >= %{minimum_postgresql}
Requires(prereq):       postgresql-server >= %{minimum_postgresql}
Requires(post):         postgresql        >= %{minimum_postgresql}
Requires(post):         postgresql-server >= %{minimum_postgresql}
Requires(post):         compat-libstdc++

# chkconfig
Requires(post):         /sbin/chkconfig
Requires(preun):        /sbin/chkconfig
---(chomp)---

Hope that's useful to people.  At the very least *I* now know I can 
refer back to it in the list archives.  <grin>

-- 
[ Benjamin Reed a.k.a. Ranger Rick ]   [ http://ranger.befunk.com/ ]
"In the pants of peace, there will always be pockets of resistance."
                                     -- Fake Geraldo on Conan O'Brien