Acido is an utility and testbed to manipulate App Container Images. I don't know if it will become a real project or just a testbed to implement features for Rocket.
I started with the idea to build Images with a simple build language (like a DockerFile, but only the build parts as the remaining parts are implemented by the appc spec).
For doing this some basic features were needed:
- Extract aci images satisfying all dependencies
- Create new aci images containing only the changes from a base image
- Copy and extract files inside the container (like Dockerfile ADD and COPY commands).
- Executes commands inside the container (like Dockerfile RUN command)
By now the first 2 point are implemented and you can create and manage new images starting from a base image.
By now with the extract
and startbuild
commands the image is fetched from the Rocket CAS store by ImageID. In future there will be a way to get an image also by its name and labels (rkt/rkt#395).
Note: By now rocket is waiting for PR to implements various features:
- An aci renderer that is able to build an image with dependencies (rkt/rkt#464, rkt/rkt#465, rkt/rkt#533). So, as today, generated ACIs that have dependencies cannot be used.
- A way to get images from the cas by an ImageID or by a app name and optional labels (rkt/rkt#392, rkt/rkt#393, rkt/rkt#394, rkt/rkt#395, rkt/rkt#322).
As of now, some parts of this program have been proposed for coreos/rocket and appc/spec (tar package new features and fixes, acirenderer etc...), other are going to be proposed (ACIBuilder, FSDiffer etc...)
$ wget 'https://github.com/fedora-cloud/docker-brew-fedora/blob/b252b53a976a0e908805d59fb7250e8d5072f4e8/fedora-21-release.tar.xz?raw=true' -O /tmp/fedora-21-release.tar.xz
mkdir -p /tmp/fedora21/rootfs
cd /tmp/fedora21/rootfs
tar xvf /tmp/fedora-21-release.tar.xz
Create a manifest file for this aci:
$ cat /tmp/fedora21/manifest
{
"acKind": "ImageManifest",
"acVersion": "0.3.0",
"name": "example.com/fedora",
"labels": [
{
"name": "version",
"value": "21.0.0"
},
{
"name": "arch",
"value": "amd64"
},
{
"name": "os",
"value": "linux"
}
]
}
$ ./acido build /tmp/fedora21/ /tmp/fedora21.aci
$ ./acido import /tmp/fedora21.aci
INFO import.go:47: image: /tmp/fedora21.aci, hash: sha512-34e79f60f57fe90951612975651562349ac5be20bef2ba8f9dd4900794d1647c
The returned hash value will be used in the next operations (until the discovery mechanism is implemented)
$ ./acido startbuild sha512-34e79f60f57fe90951612975651562349ac5be20bef2ba8f9dd4900794d1647c
INFO startbuild.go:39: tmpdir: /tmp/645016202
INFO startbuild.go:52: Image extracted to /tmp/645016202
This will extract the requested image and create a base manifest with the dependencies already defined to the extracted image.
$systemd-nspawn -D /tmp/645016202/rootfs /bin/bash
Spawning container rootfs on /tmp/167589206/rootfs.
Press ^] three times within 1s to kill container.
$ yum -y install grep
[...]
$ yum -y remove firewalld
[...]
Container rootfs terminated by signal KILL.
./acido build /tmp/645016202 /tmp/fedora21-new.aci
A new image will be created containing only the diffs from the dependencies.
./acido import /tmp/fedora21-new.aci
INFO import.go:47: image: /tmp/fedora21-new.aci, hash: sha512-7faaf487ee92c4b8efb4a2148a98866de601cdac8f4ddb519e6213e4c3d52c4e
./acido extract sha512-7faaf487ee92c4b8efb4a2148a98866de601cdac8f4ddb519e6213e4c3d52c4e
You can test with a diff -r -q that the new extracted image directory rebuilt from its dependencies matches the directory used by the build in the previous step.