#318 Add docs on how fedora builds OSTrees.
Merged 4 years ago by dustymabe. Opened 4 years ago by dustymabe.
dustymabe/atomic-wg dusty  into  master

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+ # How Do We Create OSTree Repos and Artifacts in Fedora

+ 

+ # Introduction

+ 

+ **NOTE:** For background on OSTree check out the

+           [docs](https://ostree.readthedocs.io/en/latest/).

+ 

+ When you want to create a new OSTree using `rpm-ostree` you usually define

+ a few yum repos, and then a json file that says what rpms you

+ want to be composed in the tree. You then run an `rpm-ostree compose

+ tree` command to create the commit in the ostree repo. Once the

+ ostree commit has been created you can then create installer images

+ (ISOs) and cloud/VM images (qcow, etc) from that ostree.

+ 

+ How does Fedora do this? It's a bit complicated, but I'll try to cover

+ the bases. 

+ 

+ First I'll give you a little high level view of the way things are

+ built before major release, all using Pungi. I'll then try to dig into

+ *The LEGOs* that are used to build the artifacts we care about.

+ Finally, I'll try to explain how things are different after a major

+ release is out and how we end up getting updated rpms and eventually

+ two week releases out the door.

+ 

+ 

+ # Before Fedora Major Release: Building Everything Using Pungi

+ 

+ Prior to any major release of Fedora the release engineering team *builds the

+ whole world* every night. This is done using a tool called

+ [Pungi](https://pagure.io/pungi). A [script](https://pagure.io/pungi-fedora/blob/392bc7589ecff19e91e03cef34265a270514745e/f/nightly.sh)

+ is called to kick off the nightly run via a [cron job](https://infrastructure.fedoraproject.org/cgit/ansible.git/tree/roles/releng/files/branched). 

+ The Pungi config that is used is the [fedora.conf](https://pagure.io/pungi-fedora/blob/392bc7589ecff19e91e03cef34265a270514745e/f/fedora.conf)

+ file from the [pungi-fedora](https://pagure.io/pungi-fedora) git repo. 

+ 

+ For Fedora 26 you can see where the ostree for Atomic Host is defined

+ in the Pungi config, [here](https://pagure.io/pungi-fedora/blob/392bc7589ecff19e91e03cef34265a270514745e/f/fedora.conf#_710-728),

+ in the **ostree** section. During a compose you can

+ see that the ostree will get placed into `"ostree_repo": "/mnt/koji/compose/atomic/26/",`.

+ After the compose has finished it will get synced to `/mnt/koji/atomic/26/` which corresponds

+ to the public URL https://kojipkgs.fedoraproject.org/atomic/26/.

+ 

+ During the compose, once the ostree commit has been created, the

+ installer ISO and the cloud images can get created. The definition for

+ the [installer ISO](https://pagure.io/pungi-fedora/blob/392bc7589ecff19e91e03cef34265a270514745e/f/fedora.conf#_741-761)

+ and the [cloud images](https://pagure.io/pungi-fedora/blob/392bc7589ecff19e91e03cef34265a270514745e/f/fedora.conf#_355-383)

+ are all within the same Pungi config.

+ 

+ # The LEGOs 

+ 

+ There are a few building blocks we need to talk about before we really jump into

+ how this whole thing is put together. First, we have to talk about how the OSTree

+ gets created and then the artifacts that are derived from it.

+ 

+ ## The RPM OSTree

+ 

+ To create the OSTree Pungi ends up calling out to a [Koji](https://pagure.io/koji)

+ runroot task. This runroot task essentially runs a command and harvests the results. The

+ command that eventually gets run is an [rpm-ostree command](https://pagure.io/pungi/blob/381d08a81079581595e9e48174267b7e7bbd263b/f/pungi/ostree/tree.py#_31-32)

+ that looks something like this:

+ 

+ ```nohighlight

+ rpm-ostree compose tree --repo=/mnt/koji/compose/atomic/26/ \

+ --write-commitid-to=/mnt/koji/compose/branched/Fedora-26-20170705.n.0/logs/x86_64/Atomic/ostree-2/commitid.log \

+ /mnt/koji/compose/branched/Fedora-26-20170705.n.0/work/ostree-2/config_repo/fedora-atomic-docker-host.json

+ ```

+ 

+ From the [ostree part of the Pungi config](https://pagure.io/pungi-fedora/blob/392bc7589ecff19e91e03cef34265a270514745e/f/fedora.conf#_710-728)

+ you can see where some of the arguments for this command came from:

+ 

+ ```

+ ostree = [

+     ("^Atomic$", {

+         "x86_64": {

+             "treefile": "fedora-atomic-docker-host.json",

+             "config_url": "https://pagure.io/fedora-atomic.git",

+             "config_branch": "f26",

+             "source_repo_from": "Everything",

+             "ostree_repo": "/mnt/koji/compose/atomic/26/",

+             'failable': ['*'],

+         }

+     }),

+ ```

+ 

+ We store our inputs inputs to `rpm-ostree compose tree` in 

+ the [fedora-atomic](https://pagure.io/fedora-atomic.git) git repo. The 

+ [fedora-26.repo](https://pagure.io/fedora-atomic/blob/d79a03ecf213843d2cbff2145c88865d3e898183/f/fedora-26.repo) 

+ file defines the dnf repositories and the 

+ [fedora-atomic-host.json]([https://pagure.io/fedora-atomic/blob/d79a03ecf213843d2cbff2145c88865d3e898183/f/fedora-atomic-host.json)

+ file defines which of those repositories to use, which rpms to pull

+ from them, and a few other things.

+ 

+ 

+ ## The Installer ISO

+ 

+ For the installer ISO Pungi again calls out to a Koji runroot task. The

+ command that eventually gets run is a [lorax](https://github.com/rhinstaller/lorax)

+ command that looks something like this:

+ 

+ ```nohighlight

+ lorax --product=Fedora --version=26 --release=20170705.n.0 \

+ --source=http://kojipkgs.fedoraproject.org/compose/branched/Fedora-26-20170705.n.0/compose/Everything/x86_64/os \

+ --variant=Atomic --nomacboot --volid=Fedora-Atomic-ostree-x86_64-26 \

+ --installpkgs=fedora-productimg-atomic \

+ --add-template=/mnt/koji/compose/branched/Fedora-26-20170705.n.0/work/x86_64/Atomic/lorax_templates/ostree-based-installer/lorax-configure-repo.tmpl \

+ --add-template=/mnt/koji/compose/branched/Fedora-26-20170705.n.0/work/x86_64/Atomic/lorax_templates/ostree-based-installer/lorax-embed-repo.tmpl \

+ --add-template-var=ostree_install_repo=https://kojipkgs.fedoraproject.org/compose/atomic/26/ \

+ --add-template-var=ostree_update_repo=https://kojipkgs.fedoraproject.org/atomic/26/ \

+ --add-template-var=ostree_osname=fedora-atomic \

+ --add-template-var=ostree_install_ref=fedora/26/x86_64/atomic-host \

+ --add-template-var=ostree_update_ref=fedora/26/x86_64/atomic-host \

+ --logfile=/mnt/koji/compose/branched/Fedora-26-20170705.n.0/logs/x86_64/Atomic/ostree_installer-1/lorax.log \

+ --rootfs-size=3 /mnt/koji/compose/branched/Fedora-26-20170705.n.0/work/x86_64/Atomic/ostree_installer

+ ```

+ 

+ From the [installer ISO](https://pagure.io/pungi-fedora/blob/392bc7589ecff19e91e03cef34265a270514745e/f/fedora.conf#_741-761)

+ part of the Pungi config you can see some configuration that was set

+ and eventually translated into the lorax command above.

+ 

+ ```

+ ostree_installer = [

+     ("^Atomic$", {

+         "x86_64": {

+             "source_repo_from": "Everything",

+             "release": None,

+             "rootfs_size": "3",

+             "installpkgs": ["fedora-productimg-atomic"],

+             "add_template": ["ostree-based-installer/lorax-configure-repo.tmpl",

+                              "ostree-based-installer/lorax-embed-repo.tmpl"],

+             "add_template_var": [

+                 "ostree_install_repo=https://kojipkgs.fedoraproject.org/compose/atomic/26/",

+                 "ostree_update_repo=https://kojipkgs.fedoraproject.org/atomic/26/",

+                 "ostree_osname=fedora-atomic",

+                 "ostree_install_ref=fedora/26/x86_64/atomic-host",

+                 "ostree_update_ref=fedora/26/x86_64/atomic-host",

+             ],

+             'template_repo': 'https://pagure.io/fedora-lorax-templates.git',

+             'template_branch': 'f26',

+             'failable': ['*'],

+         }

+     }),

+ ```

+ 

+ There are a few lorax templates we are passing in as well as some variables

+ to those templates. The templates are stored in the [fedora-lorax-templates](https://pagure.io/fedora-lorax-templates.git)

+ git repo.

+ 

+ 

+ ## The Cloud Images

+ 

+ For the cloud images Koji has higher level support for building

+ them than it does for the installer ISO or for creating the ostree.

+ It doesn't need to run things in a runroot, which is generic, but

+ rather it can create an ImageBuild task to create an image.

+ 

+ This is still all defined in the Pungi config. The `image-build` sections

+ for Atomic Host are [here](https://pagure.io/pungi-fedora/blob/392bc7589ecff19e91e03cef34265a270514745e/f/fedora.conf#_355-383)

+ in the Pungi config. One of these sections looks like:

+ 

+ ```

+ 	'image-build': {

+ 			'format': [('qcow2','qcow2'), ('raw-xz','raw.xz')],

+ 			'name': 'Fedora-Atomic',

+ 			'kickstart': 'fedora-atomic.ks',

+ 			'distro': 'Fedora-22',

+ 			'disk_size': 6,

+ 			'arches': ['x86_64'],

+ 			'install_tree_from': 'Cloud',

+ 			'subvariant': 'Atomic',

+ 			'failable': ['*'],

+ 	}

+ ```

+ 

+ You'll notice that we say what kickstart file to use, but we don't define

+ where to pull the kickstart file from. The git repo for the kickstarts is

+ defined along with a few other varialbes [earlier in the file](https://pagure.io/pungi-fedora/blob/392bc7589ecff19e91e03cef34265a270514745e/f/fedora.conf#_266-271).

+ 

+ # After Fedora Major Release: Bodhi + Pungi + Release

+ 

+ Once Fedora is officially released for a particular version there is a

+ *release day* yum/dnf repository that is made from the rpms that were

+ stable on the day of release. This repository is frozen and will not

+ change.

+ 

+ There are two more repositories that become significant now. These are

+ the **updates** and the **updates-testing** repositories. The **updates**

+ repo contains packages that have passed testing and are available to Fedora users

+ whenever they run `dnf update`. The **updates-testing** repo is for

+ packages that have been built and have been submitted as an update for

+ people to test to make sure nothing is broken before graduating to **updates**.

+ The **updates-testing** repo is not enabled by default. A user would

+ have to willingly enable it for the purpose of doing testing.

+ 

+ All of that is to say that there are other repos that exist after

+ release day that are for updated rpms.

+ 

+ ## Bodhi

+ 

+ Within Fedora there is a tool known as [Bodhi](https://bodhi.fedoraproject.org/)

+ that is responsible for tracking what state particular packages are in

+ and moving them between the **updates** and **updates-testing** repos.

+ As part of this, Bodhi is currently responsible for creating the

+ repositories and also the OSTree commits from the new content that

+ it just created a repo for. Bodhi was the most logical candidate for

+ this at the time it was implemented because we wanted to create a new

+ commit as soon as we could grab new content (right after the

+ repositories are created).

+ 

+ After creating the OSTree content it gets synced to `fedora/26/x86_64/updates/atomic-host`

+ ref within the OSTree repository at https://kojipkgs.fedoraproject.org/atomic/26/.

+ This is a global location/ref that users could pull from for existing

+ installed systems.

+ 

+ ## Pungi

+ 

+ When Bodhi runs and creates a new **updates** repo it also creates a

+ new OSTree. When we do an official two week release we release other

+ artifacts (ISOs, Qcows, etc) too. These get built once a day and uses the 

+ [fedora-atomic.conf](https://pagure.io/pungi-fedora/blob/392bc7589ecff19e91e03cef34265a270514745e/f/fedora-atomic.conf)

+ Pungi config (which gets called from the 

+ [twoweek-nightly.sh](https://pagure.io/pungi-fedora/blob/392bc7589ecff19e91e03cef34265a270514745e/f/twoweek-nightly.sh)

+ script). Basically the config creates repos from the `f26-atomic` Koji tag

+ which inherits from the `f26` tag (release day tag). It creates some 

+ repos from rpms in the `Cloud` variant and then builds installer

+ images and qcows based on those rpms. The installer images and the

+ qcows actually pull the OSTree from the commit that was generated

+ by the last Bodhi run, though. So the yum/dnf repository created

+ during the Pungi run only affects the installer, not the installed 

+ OSTree in the installed systems.

+ 

+ ## Performing A Two Week Atomic Host Release

+ 

+ So with the OSTree created by Bodhi and the other artifacts created by

+ Pungi we can now test do an official two week Atomic Host release.

+ This is currently run by a member of releng and the process is

+ documented by [this](https://docs.pagure.org/releng/sop_two_week_atomic.html)

+ Standard Operating Procedure guide. It eventually tells the operator

+ to run [this releng script](https://pagure.io/releng/blob/e1fa88d3937412ca0f3c5d166f1b82c5106b1256/f/scripts/push-two-week-atomic.py)

+ to do the release. The script does several things but most noteworthy

+ is updating the `fedora/26/x86_64/atomic-host` ref within the OSTree

+ repo, syncing out the ISOs/qcows to the mirrors, and updating the

+ [website](https://getfedora.org/atomic/download/).

+ 

+ # Conclusion

+ 

+ Our processes differ slightly for before and after Fedora release.

+ The entire pipeline involves Koji, Bodhi, and Pungi, and many tools

+ underneath the covers. There is a lot of working being done to try to improve these

+ processes including [calling Pungi from Bodhi](https://pagure.io/atomic-wg/issue/300)

+ in the short term and possibly [building Atomic Host from a Module](https://pagure.io/atomic-wg/issue/312)

+ in the longer term. Please reach out to us with any questions about

+ this whole process in #atomic on freenode.

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