Wednesday, June 22, 2016

Repair YUM on Oracle Linux

Whenever playing with Oracle Linux and trying out things on test systems you will break stuff at one point in time. As long as you except the fact that stuff might break when you try out new things this is not an issue. As long as you understand that production systems are not play systems there is also no issue. I recently hit an issue when I was trying to find ways to do an upgrade of Python. Even though all looked fine in the beginning I found out that it actually killed the way how some python scripts react. And more specifically how yum (a python script) reacted.

When trying to install some additional packages for another project by using yum the error message I received stated the below:

There was a problem importing one of the Python modules
required to run yum. The error leading to this problem was:

   No module named yum

Please install a package which provides this module, or
verify that the module is installed correctly.

It's possible that the above module doesn't match the
current version of Python, which is:
2.7.6 (default, Jun 14 2016, 09:18:35)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-17)]

If you cannot solve this problem yourself, please go to
the yum faq at:
  http://yum.baseurl.org/wiki/Faq


As it turns out the, yum is not able to work with the newer version of python that has become my standard python version (which I needed for Tensorflow). The issue can be resolved by calling the previous version explicitly.

If you check the content of /usr/bin/yum this will be as shown below:

#!/usr/bin/python
import sys
try:
    import yum
except ImportError:
    print >> sys.stderr, """\
There was a problem importing one of the Python modules
required to run yum. The error leading to this problem was:

   %s

Please install a package which provides this module, or
verify that the module is installed correctly.

It's possible that the above module doesn't match the
current version of Python, which is:
%s

If you cannot solve this problem yourself, please go to
the yum faq at:
  http://yum.baseurl.org/wiki/Faq

""" % (sys.exc_value, sys.version)
    sys.exit(1)

sys.path.insert(0, '/usr/share/yum-cli')
try:
    import yummain
    yummain.user_main(sys.argv[1:], exit_code=True)
except KeyboardInterrupt, e:
    print >> sys.stderr, "\n\nExiting on user cancel."
    sys.exit(1)

As can be seen, the default version is called, by changing this to the previous version (do note my other blogpost on Python) you can repair yum again. After changing the first line to the one below yum worked again without any issue.

!/usr/bin/python2.6


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