ppa/git problems after installing certificates. Revert system to default?

Question

I have installed some certificates and after I did it i have a lot of problems with the ppa and git:

1. sudo apt update returns errors for missing release files where they actually are:

   server certificate verification failed. CAfile: /etc/ssl/certs/ca-certificates.crt CRLfile: none
   E: The repository 'https://deb.opera.com/opera-stable/dists/stable stable Release' does not have a Release file.
   N: Updating from such a repository can't be done securely, and is therefore disabled by default.
   

But if you follow the link above you will see that there is a Release file.

2. adding a repository via terminal results in this message, no matter what user/ppa I try to add:

   Cannot add PPA: 'ppa:~teejee2008/ubuntu/ppa'.
   ERROR: '~teejee2008' user or team does not exist.
   

3. git pull origin master

   fatal: unable to access 'https://path-to-repository.git/': server certificate verification failed. CAfile: /etc/ssl/certs/ca-certificates.crt CRLfile: none
   

A workaround here is to set export GIT_SSL_NO_VERIFY=1, but it is not a nice solution.

Because the certificates I have already installed are not necessary anymore, is it possible to revert the certificate system to default without reinstalling the elementary OS?

Answer 1

The problem comes after installing some certificates, and did not resolve when I removed them, not even using sudo apt-get install --reinstall ca-certificates or sudo dpkg-reconfigure ca-certificates.

The solution I found was to completely remove the ca-certificates package and install it again, instead of using --reinstall.

sudo apt remove --purge ca-certificates
sudo apt autoremove
sudo apt install ca-certificates

and because the autoremove removed software-properties-common, I have to install it again by typing

sudo apt install software-properties-common

After these steps I can add repositories, use git pull and sudo apt update without any problems.