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Cob

Cob, yet another yum S3 plugin, provides a way to accessing yum repositories hosted on AWS S3.

What's the difference between Cob and original yum s3 plugin?

  • Support more secure AWS Signature Version 4 while original one still in version 2, especially for the new region eu-central-1 only SigV4 allowed
  • Hook on higher layer of Yum built-in library to avoid complicated low-level handlings
  • Support static AWS credentials prior to IAM role
  • Add retry mechanism to fetch IAM role credentials

Quick Start

  • Installation

    • ./install.sh
    • plugin conf: cob.conf --> /etc/yum/pluginconf.d/cob.conf
    • plugin code: cob.py --> /usr/lib/yum-plugins/cob.py
  • Setup minimal IAM Role Policy for Cob

    {
      "Statement": [
        {
          "Effect": "Allow",
          "Action": [
            "s3:GetObject"
          ],
          "Resource": "*"
        }
      ]
    }
    • For cross-account access, setup the policy of yum s3 bucket

      {
        "Version": "2008-10-17",
        "Statement": [
          {
            "Effect": "Allow",
            "Principal": {
              "AWS": [
                "arn:aws:iam::37ABC0340XYZ:root",
                "arn:aws:iam::24ABC3058XYZ:root"
              ]
            },
            "Action": "s3:GetObject",
            "Resource": "arn:aws:s3:::yum-s3-bucket-XYZ/*"
          }
        ]
      }
      • "37ABC0340XYZ", "24ABC3058XYZ": AWS account id with the permission to access
      • "yum-s3-bucket-XYZ": S3 bucket for yum access
  • Configure your yum repo conf under /etc/yum.repos.d/, like the example below cob.repo

    [cob]
    name=cob
    baseurl=https://your-bucket-name-0.s3.amazonaws.com/repo-name/arch/
            https://your-bucket-name-1.s3-eu-west-1.amazonaws.com/repo-name/arch/
            https://your-bucket-name-2.s3-us-west-2.amazonaws.com/repo-name/arch/
    failovermethod=priority
    enabled=1
    gpgcheck=0
  • An example from cob.conf is taken to indicate its usages:

    [main]
    cachedir=/var/cache/yum/$basearch/$releasever
    keepcache=1
    debuglevel=4
    logfile=/var/log/yum.log
    exactarch=1
    obsoletes=0
    gpgcheck=0
    plugins=1
    distroverpkg=centos-release
    enabled=1
    
    [aws]
    # access_key = 
    # secret_key =
    timeout = 60
    retries = 5
    metadata_server = http://169.254.169.254
    • set main/enabled=1 to enable this yum plugin
    • for static AWS credentials, you could specify via aws/access_key, aws/secret_key
    • aws/timeout and aws/retries, used to indicate params in the way of fetching IAM role credentials
    • metadata_server used to help testing
  • Enable verbose log to help troubleshoot the Cob issue:

    URLGRABBER_DEBUG=1 yum -v makecache