CAcert is a free (gratis, free of charge) root certificate trusted by many sites and many distributions and programs. There has been talk about inclusion in ubuntu in 2005 in an UbuntuDownUnder BoF but ultimately didn't happen.


You can manually install the CAcert root certificate with the following command:

sudo apt-get install ca-cacert

The file will be installed in


But you need to manually import it. Firefox used to allow the import to start from command line, but now this has to be done in Preferences -> Advanced -> View Certificates.

If you are still getting a message like You have not chosen to trust "Thwate Premium Server CA" you will need to manually copy the SSL Certificate to the ICAClinet directory.

  1. Go into Firefox → Edit → Preferences → Advanced → View Certificates → Authorities Tab
  2. Find the missing certificate, e.g. Thwate Premium Server CA
  3. Export this Certificate to your hard drive somewhere
  4. Run the following command (assuming you Exported to your Downloads directory) to copy the file to the ICAClient directory:

    cp ~/Downloads/ThawtePremiumServerCA /usr/lib/ICAClient/keystore/cacerts

CAcert (last edited 2019-04-15 12:54:01 by zhangweiwu)