ec2-init overwrites user/vmbuilder provided /etc/apt/sources.list

Binary package hint: ec2-init

The ec2-init startup code in /usr/bin/ec2-set-defaults overwrites the /etc/apt/sources.list that was bundled with the image.

I support the goal of this code, which is to provide a reasonable default of an apt mirror in the same EC2 region where the instance is running, but the end effect is disastrous for people and tools attempting to create custom /etc/apt.sources.list files on EC2 images.

The (undocumented?) workaround for this problem was for the image builder to place their desired sources.list into the file:

    /etc/ec2-init/templates/sources.list.tmpl

However,

a. it is unintuitive and difficult for image builders to know they should do this, and

b. this does not interact well with even the existing image building software like vmbuilder.

Here are some use cases which are hurt by the current policy of always overwriting:

1. User sets the image /etc/apt/sources.list to point to a daily snapshot in the Ubuntu EC2 mirror provided by RightScale.

2. User adds multiverse to an EC2 image they are building using vmbuilder's --components option.

3. User adds a PPA to an EC2 image they are building using vmbuilder's --ppa option.

All of the above preferences in the image are currently wiped out by ec2-init when the EC2 instance boots up.

I'd like to see ec2-init be able to detect when the user has customized the /etc/apt/sources.list and not overwrite it. This seems like it would offer the smallest element of surprise and require the least amount of ongoing user frustration and support effort.

Further enhancements could then be made to vmbuilder so that its basic --component and --ppa options integrate nicely with the new ec2-init. For example:

1. vmbuilder --component could be smart and modify the /etc/ec2-init/templates/sources.list.tmpl in addition to /etc/apt/sources.list and could communicate to ec2-init that the /etc/apt/sources.list may be overwritten with ones generated from the templates using the current EC2 region.

2. vmbuilder --ppa could create a file like /etc/apt/sources.list.d/[PPANAME]-ppa.list instead of appending lines to the /etc/apt/sources.list file.

The vmbuilder --mirror option would still create a custom /etc/apt/sources.list file which should not be overwritten by ec2-init.

ProblemType: Bug
Architecture: i386
Date: Sun Jan 3 00:36:20 2010
DistroRelease: Ubuntu 9.10
Ec2AMI: ami-1515f67c
Ec2AMIManifest: ubuntu-images-us/ubuntu-karmic-9.10-i386-server-20091027.1.manifest.xml
Ec2AvailabilityZone: us-east-1a
Ec2InstanceType: c1.medium
Ec2Kernel: aki-5f15f636
Ec2Ramdisk: ari-0915f660
Package: ec2-init 0.4.999-0ubuntu7
PackageArchitecture: all
ProcEnviron:
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcVersionSignature: User Name 2.6.31-302.7-ec2
SourcePackage: ec2-init
Tags: ec2-images
Uname: Linux 2.6.31-302-ec2 i686