Failed to Synchronize Cache For Repo 'repo_name', Ignoring This Repo.

The Problem

While installing package or listing using dnf or yum commands getting below errors:

# dnf repolist
Oracle Linux 8 Application Stream (x86_64) 0.0 B/s | 0 B 00:02
Oracle Linux 8 BaseOS Latest (x86_64) 0.0 B/s | 0 B 00:02
Failed to synchronize cache for repo 'ol8_appstream', ignoring this repo.
Failed to synchronize cache for repo 'ol8_baseos_latest', ignoring this repo.

# tail -f /var/log/dnf.log
2019-08-12T10:58:13Z INFO --- logging initialized ---
2019-08-12T10:58:13Z DDEBUG timer: config: 3 ms
2019-08-12T10:58:13Z DEBUG Loaded plugins: builddep, changelog, config-manager, copr, debug, debuginfo-install, download, generate_completion_cache, needs-restarting, playground, repoclosure, repodiff, repograph, repomanage, reposync
2019-08-12T10:58:13Z DEBUG DNF version: 4.0.9
2019-08-12T10:58:13Z DDEBUG Command: dnf repolist
2019-08-12T10:58:13Z DDEBUG Installroot: /
2019-08-12T10:58:13Z DDEBUG Releasever: 8
2019-08-12T10:58:13Z DEBUG cachedir: /var/cache/dnf
2019-08-12T10:58:13Z DDEBUG Base command: repolist
2019-08-12T10:58:13Z DDEBUG Extra commands: ['repolist']
2019-08-12T10:58:13Z DEBUG repo: downloading from remote: ol8_appstream
2019-08-12T10:58:16Z DEBUG Cannot download 'https://yum.oracle.com/repo/OracleLinux/OL8/appstream/x86_64/': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried.
2019-08-12T10:58:16Z DEBUG repo: downloading from remote: ol8_baseos_latest
2019-08-12T10:58:18Z DEBUG Cannot download 'https://yum.oracle.com/repo/OracleLinux/OL8/baseos/latest/x86_64': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried.
2019-08-12T10:58:18Z WARNING Failed to synchronize cache for repo 'ol8_appstream', ignoring this repo.
2019-08-12T10:58:18Z WARNING Failed to synchronize cache for repo 'ol8_baseos_latest', ignoring this repo.
2019-08-12T10:58:18Z DEBUG No module defaults found
2019-08-12T10:58:18Z DDEBUG timer: sack setup: 5157 ms
2019-08-12T10:58:18Z DEBUG Total packages: 0
2019-08-12T10:58:18Z DDEBUG Cleaning up.

The Solution

There sould me multiple reasons for this issue. The most common ones are:

• Incorrect date and time settings
• Old dnf cache available or expired
• Proxy address not defined or incorrect proxy address provided in /etc/dnf/dnf.conf

1. Check the date and time of this server and ensure its current.

# timedatectl

or

# date

2. Clear the expired or old cache using the below command.

# dnf clean all

3. Update correct proxy address in /etc/dnf/dnf.conf file, then its ability to install and list packages.

# cat /etc/dnf/dnf.conf
[main]
gpgcheck=1
installonly_limit=3
clean_requirements_on_remove=True
best=True
proxy=http://[proxy-host].[domain].com:[port]

# dnf repolist
Oracle Linux 8 Application Stream (x86_64) 403 kB/s | 9.6 MB 00:24
Oracle Linux 8 BaseOS Latest (x86_64) 394 kB/s | 5.4 MB 00:13
Last metadata expiration check: 0:00:02 ago on Mon 12 Aug 2019 04:42:02 PM IST.
repo id repo name status
ol8_appstream Oracle Linux 8 Application Stream (x86_64) 7,784
ol8_baseos_latest Oracle Linux 8 BaseOS Latest (x86_64) 2,595

# dnf install ksh
Last metadata expiration check: 0:00:52 ago on Mon 12 Aug 2019 04:42:02 PM IST.
Dependencies resolved.
===================================================================================================
Package Arch Version Repository Size
===================================================================================================
Installing:
ksh x86_64 20120801-252.0.1.el8 ol8_appstream 928 k
Transaction Summary
===================================================================================================
Install 1 Package
Total download size: 928 k
Installed size: 3.5 M
Is this ok [y/N]: y
Downloading Packages:
ksh-20120801-252.0.1.el8.x86_64.rpm 129 kB/s | 928 kB 00:07
---------------------------------------------------------------------------------------------------
Total 129 kB/s | 928 kB 00:07
warning: /var/cache/dnf/ol8_appstream-d4d5cd0a0a095846/packages/ksh-20120801-252.0.1.el8.x86_64.rpm: Header V3 RSA/SHA256 Signature, key ID ad986da3: NOKEY
Oracle Linux 8 Application Stream (x86_64) 3.0 MB/s | 3.1 kB 00:00
Importing GPG key 0xAD986DA3:
Userid : "Oracle OSS group (Open Source Software group) <build@oss class="oracle com">"
Fingerprint: 76FD 3DB1 3AB6 7410 B89D B10E 8256 2EA9 AD98 6DA3
From : /etc/pki/rpm-gpg/RPM-GPG-KEY-oracle
Is this ok [y/N]: y
Key imported successfully
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
Preparing : 1/1
Installing : ksh-20120801-252.0.1.el8.x86_64 1/1
Running scriptlet: ksh-20120801-252.0.1.el8.x86_64 1/1
Verifying : ksh-20120801-252.0.1.el8.x86_64 1/1
Installed:
ksh-20120801-252.0.1.el8.x86_64

Complete!</build@oss>