Error: Failed to synchronize cache for repo 'fedora'

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Problem could be that the server does currently doesn't provide the repository as configured:

If you go here http://download.fedoraproject.org/pub... , you will see that there is only a folder test (for F24_Alpha & F24_beta), but no folder 24

If $releasever in your fedora.repo points to 24 (instead of test/24_Beta), dnf will just not find the repo and its metadata.

As a quick workaround, you can comment (#) the existing baseurl line an add the following (in fedora.repo and fedora-updates.repo):

baseurl=http://download.fedoraproject.org/pub/fedora/linux/releases/test/24_Beta/Everything/$basearch/os/

dnf may have problems if you are using some proxy configurations.

So if you are using, edit the file /etc/dnf/dnf.conf. Add the follow lines: proxy=http://192.168.0.1:8080 proxy_username=proxy.user proxy_password=myproxypassword

If you are using a specific proxy, just add the follow line with you proxy adress and port: proxy=http://{adress}:{port}

After this try to run some dnf install/search command. For example: dnf install nano

Please check if update URL's are resolving properly and DNS is working. I had this issue due to DNS. We need better Error Reporting from DNF.

Yes, it can be DNS issue. Try checking /etc/resolv.conf and see if nameserver is set to something like 8.8.8.8.

I ran into this problem as well and it turns out /tmp was full. You can check with du -hs if it's chock full and if so, lose some things.

I have seen this issue happening in Fedora 25 as well, when DNS fails to resolve the update URL's. Maybe we need better Error Reporting from DNF.

I had this problem because I set firewall.d to accept HTTPS but not HTTP. I added HTTP and it resolved the issue.

I have nscd running. It was my problem. By doing a "ps -aux | grep nscd" and locating the process ID, perform a "kill" on that process ID number cleared up the issue. The nscd daemon restarts and behaves.

I'm guessing that nscd does not wait for the network service to fully start before it starts before caching host name to IP address entries.

There is something wrong with the trusted ciphers. FC24-25 defaults to FUTURE set of ciphers in /etc/crypto-policies/config. Changing that to default and running update-crypto-policies fixed this for me. Something is probably off in the FUTURE backends/gnutls.config.

With FUTURE even wget gets an error on the cert:

wget -p -O /dev/null "https://mirrors.fedoraproject.org/metalink?repo=updates-released-f25&arch=x86_64"
WARNING: combining -O with -r or -p will mean that all downloaded content
will be placed in the single file you specified.

--2016-11-28 13:51:25--  https://mirrors.fedoraproject.org/metalink?repo=updates-released-f25&arch=x86_64
Resolving mirrors.fedoraproject.org (mirrors.fedoraproject.org)... 209.132.181.15, 66.35.62.162, 140.211.169.196, ...
Connecting to mirrors.fedoraproject.org (mirrors.fedoraproject.org)|209.132.181.15|:443... connected.
ERROR: The certificate of ‘mirrors.fedoraproject.org’ is not trusted.
ERROR: The certificate of ‘mirrors.fedoraproject.org’ was signed using an insecure algorithm.

As per florian above, the repo isn't configured correctly due to the 'test' folder in front of the 'releases' folder. I have a vm running F24_beta and rectified the issue by modifying the baseurl as follows:

baseurl=http://download.fedoraproject.org/pub/fedora/linux/releases/test/24_beta/Everything/$basearch/os/

This allowed me to update the repo successfully. I was then prompted about updates and updates-testing and had to uncomment the baseurl for those as well (remove the '#' at the start of the line) but that may have been something peculiar to how my VM connects to the internet rather than an actual problem with those repos.