github: server certificate verification failed
Make sure first that you have certificates installed on your Debian in /etc/ssl/certs
.
If not, reinstall them:
sudo apt-get install --reinstall ca-certificates
Since that package does not include root certificates, add:
sudo mkdir /usr/local/share/ca-certificates/cacert.orgsudo wget -P /usr/local/share/ca-certificates/cacert.org http://www.cacert.org/certs/root.crt http://www.cacert.org/certs/class3.crtsudo update-ca-certificates
Make sure your git does reference those CA:
git config --global http.sslCAinfo /etc/ssl/certs/ca-certificates.crt
Jason C mentions another potential cause (in the comments):
It was the clock. The NTP server was down, the system clock wasn't set properly, I didn't notice or think to check initially, and the incorrect time was causing verification to fail.
It can be also self-signed certificate, etc. Turning off SSL verification globally is unsafe. You can install the certificate so it will be visible for the system, but the certificate should be perfectly correct.
Or you can clone with one time configuration parameter, so the command will be:
git clone -c http.sslverify=false https://myserver/<user>/<project>.git;
GIT will remember the false value, you can check it in the <project>/.git/config
file.