Centos 5 is not supported running yum will produce an error like this:
YumRepo Error: All mirror URLs are not using ftp, http[s] or file.
Solution - Update this file
Eg. Invalid release/
removing mirrorlist with no valid mirrors: /var/cache/yum/base/mirrorlist.txt
Error: Cannot find a valid baseurl for repo: base
CentOS-Base.repo
# CentOS-Base.repo
#
# The mirror system uses the connecting IP address of the client and the
# update status of each mirror to pick mirrors that are updated to and
# geographically close to the client. You should use this for CentOS updates
# unless you are manually picking other mirrors.
#
# If the mirrorlist= does not work for you, as a fall back you can try the
# remarked out baseurl= line instead.
#
#
[base]
name=CentOS-5.9 - Base
#mirrorlist=http://mirrorlist.centos.org/?release=5.9&arch=$basearch&repo=os
baseurl=http://vault.centos.org/5.9/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
#released updates
[updates]
name=CentOS-5.9 - Updates
#mirrorlist=http://mirrorlist.centos.org/?release=5.9&arch=$basearch&repo=updates
baseurl=http://vault.centos.org/5.9/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
#additional packages that may be useful
[extras]
name=CentOS-5.9 - Extras
#mirrorlist=http://mirrorlist.centos.org/?release=5.9&arch=$basearch&repo=extras
baseurl=http://vault.centos.org/5.9/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-5.9 - Plus
#mirrorlist=http://mirrorlist.centos.org/?release=5.9&arch=$basearch&repo=centosplus
baseurl=http://vault.centos.org/5.9/os/$basearch/centosplus/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
#contrib - packages by Centos Users
[contrib]
name=CentOS-5.9 - Contrib
#mirrorlist=http://mirrorlist.centos.org/?release=5.9&arch=$basearch&repo=contrib
baseurl=http://vault.centos.org/5.9/os/$basearch/contrib/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
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