古いCentOS6がtlsの問題で、エラーになる
まだCentOS6も残っていてこのエラーに合うことがいっぱいあるのでメモ。

# yum update
Loaded plugins: fastestmirror
Setting up Update Process
Loading mirror speeds from cached hostfile
http://vault.centos.org/centos/6/os/x86_64/repodata/repomd.xml: [Errno 14] problem making ssl connection
Trying other mirror.
Error: Cannot retrieve repository metadata (repomd.xml) for repository: base. Please verify its path and try again

nssをアップデートしてあげる

nss-3.14.0.0-12.el6.x86_64
↓
nss-3.44.0-7.el6_10.x86_64

# yum update
Loaded plugins: fastestmirror
Setting up Update Process
Loading mirror speeds from cached hostfile
http://vault.centos.org/centos/6/os/x86_64/repodata/repomd.xml: [Errno 14] Peer cert cannot be verified or peer cert invalid
Trying other mirror.
It was impossible to connect to the CentOS servers.
This could mean a connectivity issue in your environment, such as the requirement to configure a proxy,
or a transparent proxy that tampers with TLS security, or an incorrect system clock.
You can try to solve this issue by using the instructions on https://wiki.centos.org/yum-errors
If above article doesn't help to resolve this issue please use https://bugs.centos.org/.

Error: Cannot retrieve repository metadata (repomd.xml) for repository: base. Please verify its path and try again

# curl -k -L -O https://curl.se/ca/cacert.pem
# cp /etc/pki/tls/certs/ca-bundle.crt /etc/pki/tls/certs/ca-bundle.crt.bak
# cp cacert.pem /etc/pki/tls/certs/ca-bundle.crt