31dad50824
When checkpointing a container with --leave-running, libpod dumps the
container's memory via the OCI runtime (CRIU) first and only captures
the rootfs diff and named volumes afterwards. CRIU thaws the container
as soon as the memory dump finishes, so the processes inside the
container continue to run between the memory snapshot and the
file-system capture. As a result, the checkpoint can be inconsistent:
have CRIU images and a file system that reflect different points in time.
To fix this, we freeze the container's cgroup before invoking the OCI
runtime and thaw it again only after the checkpoint image/archive has
been written. The OCI runtime calls CRIU with the freezer cgroup and
restores it to its previous state once the dump completes, so a
container that was already frozen stays frozen across the dump and
the file system is captured at the same instant as the CRIU images.
This mirrors the approach other engines (e.g. CRI-O and containerd).
The default (stopping) checkpoint functionality is not affected by this
issue because CRIU leaves the tasks dead after the dump.
This patch also adds a regression test for the consistency of live
(--leave-running) checkpoints. The container runs a workload that
keeps an in-memory counter in sync with a value written to a file
on its root file system, maintaining the invariant that the on-disk
value never gets ahead of the in-memory counter.
Signed-off-by: Radostin Stoyanov <rstoyanov@fedoraproject.org>
(cherry picked from commit 2c7aeab70b)
Signed-off-by: Paul Holzinger <pholzing@redhat.com>
Podman Documentation
The online man pages and other documents regarding Podman can be found at Read The Docs. The man pages can be found under the Commands link on that page.
Build the Docs
Directory Structure
| Directory | |
|---|---|
| Markdown source for man pages | docs/source/markdown/ |
| man pages aliases as .so files | docs/source/markdown/links/ |
| target for output | docs/build |
| man pages | docs/build/man |
| remote linux man pages | docs/build/remote/linux |
| remote darwin man pages | docs/build/remote/darwin |
| remote windows html pages | docs/build/remote/windows |
Support files
| docs/remote-docs.sh | Read the docs/source/markdown files and format for each platform |
| docs/links-to-html.lua | pandoc filter to do aliases for html files |
| docs/use-pagetitle.lua | pandoc filter to set html document title |
Manpage Syntax
The syntax for the formatting of all man pages can be found here.
API Reference
The latest online documentation is
automatically generated by two cooperating automation systems based on committed upstream
source code. Firstly, the Publish swagger GitHub Actions workflow
builds pkg/api/swagger.yaml and uploads it to a public-facing location (Google Storage Bucket -
an online service for storing unstructured data). Second, Read The Docs
reacts to the github.com repository change, building the content for the libpod documentation
site. This site includes for the API section,
some javascript which consumes the uploaded swagger.yaml file directly from the Google
Storage Bucket.
Since there are multiple systems and local cache is involved, it's possible that updates to documentation (especially the swagger/API docs) will lag by 10-or-so minutes. However, because the client (i.e. your web browser) is fetching content from multiple locations that do not share a common domain, accessing the API section may show a stack-trace similar to the following:
If reloading the page, or clearing your local cache does not fix the problem, it is
likely caused by broken metadata needed to protect clients from cross-site-scripting
style attacks. Please notify a maintainer
so they may investigate how/why the swagger.yaml file's CORS-metadata is
incorrect, or the file isn't accessible for some other reason.
Local Testing
To build standard man pages, run make docs. Results will be in docs/build/man.
To build HTMLized man pages: Assuming that you have the dependencies installed, then also install (showing Fedora in the example):
$ sudo dnf install python3-sphinx python3-recommonmark
$ pip install sphinx-markdown-tables myst_parser
(The above dependencies are current as of 2022-09-15. If you experience problems, please see requirements.txt in this directory, it will almost certainly be more up-to-date than this README.)
After that completes, cd to the docs directory in your Podman sandbox and then do make html.
You can then preview the html files in docs/build/html with:
python -m http.server 8000 --directory build/html
...and point your web browser at http://localhost:8000/