[git] error - gpg failed to sign data

[nguyenvulong]

This is for secure signing, when you are doing something like

git commit -S -m "message"

Solution

first make sure you have register your signing key
git config --global user.signingkey YOUR_KEY
where YOUR_KEY can be retrieved by gpg --list-secret-keys --keyid-format=long

then try to reload the agent
echo RELOADAGENT | gpg-connect-agent

then re-commit. If you still get the error then kill the agent and launch it again
gpgconf --kill gpg-agent
gpgconf --launch gpg-agent

and may be reload it one more time
echo RELOADAGENT | gpg-connect-agent

finally
export GPG_TTY=$(tty)

If it does not work for you, check https://stackoverflow.com/questions/41052538/git-error-gpg-failed-to-sign-data