yum hangs and won't respond

All of this did not work with me.

Using CentOS and yum. yum hangs without an error message, at least, so it appears. Pressing Ctrl+C does not work (pressing it again and again and again does).

Several things need to be checked: - are the repositories OK? - is networking OK? - are the yum and rpm databases OK?

So, first start with the easy stuff - clean the databases:

rm -f /var/lib/rpm/__*
rpm --rebuilddb -v -v   
yum clean all

If that did not work, you can set a debug level, error level and timeout for yum in /etc/yum.conf:

debuglevel=1
errorlevel=1
timeout=1

The timeout is standard 30 seconds. So if a repository does not respond, the error takes 30 seconds to appear. Also try using yum without the plugins (like fastest mirror and priorities) with the option --noplugins. Now starting yum again should give you more info faster. Test with:

yum --verbose --noplugins info

You might get something like this:

 Config time: 0.105
 Yum Version: 3.2.22
 Setting up Package Sacks
 Loading mirror speeds from cached hostfile
 * base: mirror.nl.leaseweb.net
 * extras: mirror.nl.leaseweb.net
 * ius: mirrors.ircam.fr
 * rpmforge: mirror.nl.leaseweb.net
 * updates: mirror.nl.leaseweb.net link-to-server-repository/repomd.xml: [Errno 4] IOError: urlopen error (97, 'Address family not supported by protocol') 
 Trying other mirror.

This indicates no information can be received from the server. Try the URL that is displayed by yum (indicated above with link-to-server-repository) in your web browser. Copy&paste it from your yum response, not from this post! If you get a list, you know the repository is online.

If you get an error in your browser, try removing that repository from /etc/yum.repos.d. Try to fetch the list on your server with wget and paste the URL:

wget link-to-server-repository/repomd.xml

If this generates a timeout, then there's a problem with your firewall or proxy settings. Try to disable your firewall.

If you are running csf (ConfigServer Security and Firewall) and lfd you can disable csf with:

csf -x

Try yum again and if it works, you'll have to reconfigure your csf. Enable csf again with:

csf -e

And also check your proxy settings. You can also try to change the https in to http in the .repo files at /etc/yum.repos.d/.

You may have a DNS issue. Try to ensure you can resolve DNS records locally:

nslookup google.com

If you get an IP back from that command, you should be OK for DNS. Try then removing the fastestmirror cache and re-running your yum command:

rm -f /var/cache/yum/timedhosts.txt

I had a similar issue. It turned out to be an old DNS address in resolv.conf. I changed the IP to the correct one, and it fixed the issue.