The sign-off is a simple line at the end of the explanation for a commit. All commits needs to be signed. Your signature certifies that you wrote the patch or otherwise have the right to contribute the material. The rules are pretty simple, if you can certify the below (from developercertificate.org):
Developer Certificate of Origin
Version 1.1
Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
1 Letterman Drive
Suite D4700
San Francisco, CA, 94129
Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.
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 to every git commit message:
Signed-off-by: Joe Smith <joe.smith@example.com>
Use your real name (sorry, no pseudonyms or anonymous contributions.)
If you set your user.name and user.email git configs, you can sign your commit automatically
with git commit -s.
Note: If your git config information is set properly then viewing the git log information for your
commit will look something like this:
Author: Joe Smith <joe.smith@example.com>
Date: Thu Feb 2 11:41:15 2018 -0800
Update README
Signed-off-by: Joe Smith <joe.smith@example.com>
Notice the Author and Signed-off-by lines match. If they don't your PR will be rejected by the
automated DCO check.
Whether you are a user or contributor, official support channels include:
Before opening a new issue or submitting a new pull request, it's helpful to search the project - it's likely that another user has already reported the issue you're facing, or it's a known issue that we're already aware of. It is also worth asking on the Slack channels.