Hey, let's work through this issue you're stuck on. The key clue in your error logs is this line: 无法解析metalink链接https://mirrors.fedoraproject.org/metalink?repo=epel-7&arch=armhfp — notice it's trying to fetch the armhfp architecture repo, but CentOS 7.4 Core is almost certainly running on x86_64. That's exactly why you're hitting the "No repomd file" error. Here's how to fix it step by step:

1. Verify Your System's Actual Architecture #

First, confirm what architecture your system is using to be sure:

uname -m

You should see x86_64 as the output. If that's the case, the $basearch variable in yum is resolving incorrectly, which is pulling the wrong repo path.

2. Fix the EPEL Repo Configuration #

Edit the epel.repo file to force the correct architecture and disable the problematic metalink:

# Replace all instances of $basearch with your actual architecture (x86_64 here)
sudo sed -i 's/$basearch/x86_64/g' /etc/yum.repos.d/epel.repo
# Comment out the metalink line that's causing the error
sudo sed -i 's/^metalink/#metalink/g' /etc/yum.repos.d/epel.repo
# Uncomment the baseurl line to use the direct, valid repo path
sudo sed -i 's/^#baseurl/baseurl/g' /etc/yum.repos.d/epel.repo

If you are actually running on ARM (unlikely for CentOS 7.4 Core), replace x86_64 with your correct architecture value instead.

3. Clear Yum Cache and Rebuild #

Wipe out the old, invalid cache and generate a fresh one with the corrected config:

sudo yum clean all
sudo yum makecache

4. Install Python 3.6 #

Now you should be able to install Python 3.6 without any repo errors:

sudo yum -y install python36

Alternative: Use a Domestic EPEL Mirror (More Stable) #

If the above doesn't resolve things, switching to a domestic mirror (like Alibaba Cloud's) can avoid metalink parsing issues entirely:

1. Backup your old repo files first:

sudo mv /etc/yum.repos.d/epel.repo /etc/yum.repos.d/epel.repo.bak
sudo mv /etc/yum.repos.d/epel-testing.repo /etc/yum.repos.d/epel-testing.repo.bak

2. Create a new epel.repo with Alibaba's mirror:

sudo tee /etc/yum.repos.d/epel.repo <<EOF
[epel]
name=Extra Packages for Enterprise Linux 7 - \$basearch
baseurl=https://mirrors.aliyun.com/epel/7/\$basearch
failovermethod=priority
enabled=1
gpgcheck=1
gpgkey=https://mirrors.aliyun.com/epel/RPM-GPG-KEY-EPEL-7
EOF

3. Clean cache and install Python 3.6:

sudo yum clean all
sudo yum makecache
sudo yum -y install python36

Why Your Previous Attempts Didn't Work #

When you tried toggling baseurl/metalink comments before, you didn't address the root problem: the $basearch variable was resolving to armhfp instead of your actual system architecture. By hardcoding the correct architecture or using a mirror that handles variable resolution reliably, you eliminate the metalink parsing error entirely.

内容的提问来源于stack exchange，提问作者Jan Hamara