LinuxQuestions.org - no sure how yum clean all works

Hello,
recently I was trying to upgrade my RHEL 5.7 to 5.9. after importing the certificate, I was trying to run

Code:

yum update --security

It didnt work at the first attempt. Gave me this error:

Code:

[root@etl1001 ~]# yum update --security

Loaded plugins: downloadonly, product-id, rhnplugin, security, subscription-manager, verify

Updating Red Hat repositories.

dt-qa-rhel-x86_64-server-5.9                                        | 1.3 kB     00:00

dt-qa-rhel-x86_64-server-5.9/primary                                | 5.9 MB     00:00

dt-qa-rhel-x86_64-server-5.9                                                   16062/16062

file://var/cache/yum/dt-qa-rhel-x86_64-server-master/repodata/repomd.xml: [Errno 5] OSError: [Errno 2] No such file or directory: '/cache/yum/dt-qa-rhel-x86_64-server-master/repodata/repomd.xml'

Trying other mirror.

dt-qa-rhn-tools-rhel-x86_64-server-5.9                              | 1.1 kB     00:00

dt-qa-rhn-tools-rhel-x86_64-server-5.9/primary                      |  47 kB     00:00

dt-qa-rhn-tools-rhel-x86_64-server-5.9                                             524/524

file://var/cache/yum/dt-qa-rhn-tools-rhel-x86_64-server-master/repodata/repomd.xml: [Errno 5] OSError: [Errno 2] No such file or directory: '/cache/yum/dt-qa-rhn-tools-rhel-x86_64-server-master/repodata/repomd.xml'

Trying other mirror.

file://var/cache/yum/dt-thirdparty-master-x86_64/repodata/repomd.xml: [Errno 5] OSError: [Errno 2] No such file or directory: '/cache/yum/dt-thirdparty-master-x86_64/repodata/repomd.xml'

Trying other mirror.

dt-thirdparty-x86_64-5.9                                            |  871 B     00:00

dt-thirdparty-x86_64-5.9/primary                                    |  38 kB     00:00

dt-thirdparty-x86_64-5.9                                                           166/166

file://var/cache/yum/epel-5-x86_64-master/repodata/repomd.xml: [Errno 5] OSError: [Errno 2] No such file or directory: '/cache/yum/epel-5-x86_64-master/repodata/repomd.xml'

Trying other mirror.

Setting up Update Process

Resolving Dependencies

Limiting packages to security relevant ones

dt-qa-rhel-x86_64-server-5.9/updateinfo                             | 2.2 MB     00:00

file://var/cache/yum/dt-qa-rhel-x86_64-server-master/repodata/updateinfo.xml.gz: [Errno 5] OSError: [Errno 2] No such file or directory: '/cache/yum/dt-qa-rhel-x86_64-server-master/repodata/updateinfo.xml.gz'

Trying other mirror.

Error: failure: repodata/updateinfo.xml.gz from dt-qa-rhel-x86_64-server-master: [Errno 256] No more mirrors to try.

I was suggested to run

Code:

yum clean all

and the next thing you know, it worked.
I dont understand how can one tell from the error above that yum needs a clean up?

appreciate it in advance.