When automating system administration tasks, we often need to verify repository connectivity before proceeding with package operations. The default yum update behavior of trying multiple mirrors with long timeouts can be problematic in scripts.

The most efficient way to test connectivity is using yum with the --noplugins and -q flags:

yum --noplugins -q check-update &>/dev/null
echo $?  # Returns 0 if repos are accessible, non-zero otherwise

Here's a robust implementation for your scripts:

#!/bin/bash

check_yum_connectivity() {
    local timeout=10  # seconds
    local yum_test_cmd="yum --noplugins -q check-update"
    
    # Use timeout in case of hanging
    timeout $timeout $yum_test_cmd &>/dev/null
    return $?
}

if check_yum_connectivity; then
    echo "Yum repositories are accessible"
    # Proceed with your package operations
else
    echo "ERROR: Could not access yum repositories" >&2
    exit 1
fi

To check individual repositories while ignoring others:

yum --disablerepo="*" --enablerepo="epel" -q check-update

For environments requiring proxies, you might want to explicitly test the proxy first:

check_http_proxy() {
    local proxy=${1:-$http_proxy}
    curl -s --connect-timeout 5 --max-time 10 \
         --proxy "$proxy" http://mirrorlist.centos.org &>/dev/null
}

The --noplugins option significantly speeds up the check by skipping unnecessary plugin initialization. In testing, this reduces the check time from 20-30 seconds to typically under 5 seconds.

When automating system administration tasks, we often need to verify yum repository connectivity before proceeding with package operations. The default yum update or yum list commands can hang for minutes when network connectivity issues exist, especially when:

• Proxy settings are misconfigured
• Repository mirrors are unreachable
• DNS resolution fails
• Corporate firewalls block access

Here are three reliable methods to test yum connectivity with minimal overhead:

1. Using yum's --noplugins and --quiet Flags

yum --noplugins --quiet check-update &> /dev/null
if [ $? -eq 0 ]; then
    echo "Yum repositories accessible"
else
    echo "Yum connectivity issue detected"
fi

2. Testing Specific Repository Metadata

timeout 10 yum --disablerepo="*" --enablerepo="base" makecache &> /dev/null
case $? in
    0)   echo "Success";;
    124) echo "Timeout occurred";;
    *)   echo "Other failure";;
esac

3. Direct URL Testing with curl

For more granular control, test against actual repository URLs:

REPO_URL=$(yum repoinfo base | grep -oP 'baseurl=\\K[^ ]*')
if curl --connect-timeout 5 --silent --head "$REPO_URL/repodata/repomd.xml" | grep "200 OK" > /dev/null; then
    echo "Repository is responsive"
else
    echo "Connectivity problem"
fi

For production use, consider this robust implementation:

#!/bin/bash

check_yum_connectivity() {
    local timeout_seconds=15
    local status_file=$(mktemp)
    
    (yum --noplugins --quiet check-update &> "${status_file}") & pid=$!
    (sleep "${timeout_seconds}" && kill -HUP "${pid}") &>/dev/null & killer=$!
    
    if wait "${pid}" &>/dev/null; then
        pkill -HUP -P "${killer}"
        wait "${killer}"
        if grep -q "Error:" "${status_file}"; then
            return 1
        else
            return 0
        fi
    else
        return 124
    fi
    
    rm -f "${status_file}"
}

check_yum_connectivity
case $? in
    0) exit 0;;
    1) exit 1;;
    124) exit 2;;
esac

For tools like Ansible, create custom facts:

- name: Check yum connectivity
  shell: yum --noplugins --quiet check-update &> /dev/null
  register: yum_check
  ignore_errors: yes
  changed_when: false
  timeout: 10

- name: Set connectivity fact
  set_fact:
    yum_accessible: "{{ yum_check.rc == 0 }}"