spaceblog

Recently, Red Hat's up2date tool gained an --upgrade-to-release option, which tells it to ignore the current OS release version as found in /etc/redhat-release and use the one you specify. You can use this, then, to upgrade your install in-place to the next version.

I mean "recently" relatively; Debian's had this functionality since package management systems were invented, though up2date has had since at least the birth of RHEL ES 3.

Like most things about the Red Hat package management system, though, this doesn't just work.

up2date is at the mercy of the incomplete dependency information that is contained within the RPM database. When up2date is asked to upgrade the enture system, it chooses first to update itself, which it does by checking the dependency list for up2date, the dependencies of those dependencies, and so on, then works out how to resolve that all and downloads the required packages.

When you upgrade from RHEL ES 3 to RHEL ES 4, you get two packages: up2date and rhnlib.

rhnlib depends on functions within rhpl, which according to RPM is installed, but alas, does not contain the latest modules that rhnlib calls... you see, Red Hat have left out some vitally important version information from the package database.

up2date, having downloaded itself, then restarts itself, and fails.

[root@x up2date]# up2date --upgrade-to-release=4ES -u

Fetching Obsoletes list for channel: rhel-i386-es-4...

Fetching rpm headers...
########################################

Fetching Obsoletes list for channel: rhel-i386-es-4...

Name                                    Version        Rel
----------------------------------------------------------
up2date                                 4.4.50         4                 i386


Testing package set / solving RPM inter-dependencies...
########################################
up2date-4.4.50-4.i386.rpm:  ########################## Done.
rhnlib-1.8.1-1.p23.1.noarch ########################## Done.
New Up2date available
Preparing              ########################################### [100%]

Installing...
   1:rhnlib                 ########################################### [100%]
   2:up2date                ########################################### [100%]
warning: /etc/sysconfig/rhn/sources saved as /etc/sysconfig/rhn/sources.rpmsave
New Up2date available
The following packages were added to your selection to satisfy dependencies:

Name                                    Version        Release
--------------------------------------------------------------
rhnlib                                  1.8.1          1.p23.1

Restarting up2date
Restarting up2date
[root@x up2date]# Traceback (most recent call last):
  File "/usr/sbin/up2date", line 27, in ?
    from up2date_client import repoDirector
  File "/usr/share/rhn/up2date_client/repoDirector.py", line 5, in ?
    import rhnChannel
  File "/usr/share/rhn/up2date_client/rhnChannel.py", line 10, in ?
    import up2dateAuth
  File "/usr/share/rhn/up2date_client/up2dateAuth.py", line 5, in ?
    import rpcServer
  File "/usr/share/rhn/up2date_client/rpcServer.py", line 23, in ?
    from rhn import rpclib
ImportError: No module named rhn

Debian gets a lot of shit for its release cycle, and its alleged barriers to use, but at least it gets the basics of package management right. I can only assume that the many dollars my company gives to Red Hat for the RHEL licences and RHN subscriptions goes towards development of new icon sets and clicky user admin tools, and staff work on reliable infrastructure in their spare time after hours.

time passes

more time passes

Rolling back to the ES3 version of up2date and then attempting to upgrade other parts first, e.g. the kernel, trigger a TypeError whilst walking the dependency tree. I'm amazed that up2date was able to get as far as it did when it updated itself!

time continues to pass

So, for my own reference, and possibly yours, the complete (and maybe excessive) list of RPM Hell required to get up2date both usable and capable of upgrading the operating system follows here:

db4
gd
glibc
glibc-common
glibc-headers
glibc-utils
libselinux
libxml2
libxml2-python
popt
pyOpenSSL
python
rhnlib
rhpl
rpm
rpm-libs
rpm-python
up2date

You may need to remove some packages before installing, and specify --nodeps ("may" is just a euphemism for "you will absolutely need to"); --nodeps is an evil hack but necessary to remain mostly sane otherwise you will be downloading most of the archive. up2date will sort them out for you later when it graps all the latest packages.