Set up working environment
Although criu could be run as non-root (see Security), development is better to be done as root. For example, some tests require root. So, it would be a good idea to set up some recent Linux distro on a virtual machine.
Get the source code
The CRIU sources are tracked by Git. Official CRIU repo is at https://github.com/checkpoint-restore/criu.
The repository may contain multiple branches. Development happens in the criu-dev branch.
To clone CRIU repo and switch to the proper branch, run:
git clone https://github.com/checkpoint-restore/criu criu
cd criu
git checkout criu-dev
Compile
First, you need to install compile-time dependencies. Check Installation#Dependencies for more info.
To compile CRIU, run:
make
This should create the ./criu/criu executable.
Edit the source code
If you use ctags, you can generate the ctags file by running
make tags
When you change the source code, please keep in mind the following code conventions:
- we prefer tabs and indentations to be 8 characters width
- consider reading Linux kernel coding style.
Other conventions can be learned from the source code itself. In short, make sure your new code looks similar to what is already there.
Test your changes
CRIU comes with an extensive test suite. To check whether your changes introduce any regressions, run
make test
The command runs ZDTM Test Suite. Check for any error messages produced by it.
In case you'd rather have someone else run the tests, you can use travis-ci for your own github fork of CRIU. It will check the compilation for various supported platforms, as well as run most of the tests from the suite. See https://travis-ci.org/xemul/criu for more details.
Make a patch
To create a patch, run
git format-patch
You might need to read GIT documentation on how to prepare patches for mail submission. Take a look at http://book.git-scm.com/ and/or http://git-scm.com/documentation for details. It should not be hard at all.
Sign your work
To improve tracking of who did what, we ask you to sign off the patches that are to be emailed.
The sign-off is a simple line at the end of the explanation for the patch, which certifies that you wrote it or otherwise have the right to pass it on as an open-source patch. The rules are pretty simple: if you can certify the below:
Developer's Certificate of Origin 1.1
By making a contribution to this project, I certify that:
(a) The contribution was created in whole or in part by me and I
have the right to submit it under the open source license
indicated in the file; or
(b) The contribution is based upon previous work that, to the best
of my knowledge, is covered under an appropriate open source
license and I have the right under that license to submit that
work with modifications, whether created in whole or in part
by me, under the same open source license (unless I am
permitted to submit under a different license), as indicated
in the file; or
(c) The contribution was provided directly to me by some other
person who certified (a), (b) or (c) and I have not modified
it.
(d) I understand and agree that this project and the contribution
are public and that a record of the contribution (including all
personal information I submit with it, including my sign-off) is
maintained indefinitely and may be redistributed consistent with
this project or the open source license(s) involved.
then you just add a line saying
Signed-off-by: Random J Developer <random at developer.example.org>
using your real name (please, no pseudonyms or anonymous contributions if it possible).
Hint: you can use git commit -s to add Signed-off-by line to your
commit message. To append such line to a commit you already made, use
git commit --amend -s.
Example patch message
From: Random J Developer <random at developer.example.org> Subject: [PATCH] Short patch description Long patch description (could be skipped if patch is trivial enough) Signed-off-by: Random J Developer <random at developer.example.org> --- Patch body here
Mail patches
The patches should be sent to CRIU development mailing list, criu AT openvz.org. Note that you need to be subscribed first in order to post. The list web interface is available at https://openvz.org/mailman/listinfo/criu; you can also use standard mailman aliases to work with it.
Please make sure the email client you're using doesn't screw your patch (line wrapping and so on).
Wait for response
Be patient. Most CRIU developers are pretty busy people so if there is no immediate response on your patch — don't be surprised, sometimes a patch may fly around a week before it gets reviewed.
Continuous integration
Main article: Continuous integration
CRIU tests are run for each series sent to the mailing list. If you get a message from our patchwork that patches failed to pass the tests, you have to investigate what is wrong.
We also recommend you to enable Travis CI for your repo to check patches in your git branch, before sending them to the mailing list.