In a test server I typed “sudo yum update”, it reported errors like:
$sudo yum update Loaded plugins: branch, fastestmirror, security Setting up Update Process Bad id for repo: base.$releasever.x86_64, byte = $ 8 Bad id for repo: base.$releasever.noarch, byte = $ 8 Bad id for repo: ops.$releasever.x86_64, byte = $ 4 Bad id for repo: ops.$releasever.noarch, byte = $ 4 Loading mirror speeds from cached hostfile http://mirrors.xxx.com/centos/%24releasever/os/x86_64/repodata/repomd.xml: [Errno 14] PYCURL ERROR 22 - "The requested URL returned error: 404 Not Found" Trying other mirror. Error: Cannot retrieve repository metadata (repomd.xml) for repository: base. Please verify its path and try again<
Then I found this web in google for introducing how to get the value of "$releasever", but it does not tell us how to set "$releasever" permanently. Therefore, I have to search word like "releasever" in the source code of 'yum':
rpm -ql yum|xargs sudo grep releasever * -rn
Finally the source code in '/usr/lib/python2.6/site-packages/yum/__init__.py' comes out:
But where does 'self.conf.yumvar' get its values? The answer is '/etc/yum/vars/'. After
sudo bash -c "echo 6 > /etc/yum/vars/releasever"
My 'sudo yum update' works correctly now.