Docker: could not read CA certificate

Question

I installed Docker on Windows 10 Pro and I can't get it to work.

When I try to run hello-world I get

could not read CA certificate  

It's looking for the certificates in the machine/machines/default . However that folder didn't exist.

I created a machine called "default" (which created the above mentioned folder) but that didn't help.

Before that I created another machine called "dev" which seems to have certificates, but that doesn't seem to be helping either.

Also there are certificate files in machine/machines - I don't know if I should somehow point Docker to look in that folder (instead of machine/machines/default) ?

I'm pretty new to Docker so I might be missing something. However I've been at this all day, read the Docker documentation, tried plenty of solutions and similar answers but nothing seems to be working.

Answer 1

I had the same issue. The problem was, that I upgraded from Docker Toolbox to Docker for Windows. When you uninstall Docker Toolbox, the user-specific env variables get not removed. The following did the trick for me:

1. Uninstall Docker Toolbox.
2. Uninstall VirtualBox (You cannot use VirtualBox, as it is necessary for Docker Toolbox and Hyper-V [used by Docker for Windows] at the same time.)
3. Remove the Docker Toolbox env variables:
   • Go to Control Panel\All Control Panel Items\System.
   • Click Advanced system settings
   • Go to Advanced Tab and click Environment Variables.
   • Delete all DOCKER_* entries from System/User variables.
     • DOCKER_TLS_VERIFY
     • DOCKER_CERT_PATH
     • DOCKER_HOST
     • DOCKER_TOOLBOX_INSTALL_PATH

4. Remove DOCKER_* from command-prompt or PowerShell. Run these command in PowerShell:

   [Environment]::SetEnvironmentVariable("DOCKER_CERT_PATH", $null, "User")

   [Environment]::SetEnvironmentVariable("DOCKER_HOST", $null, "User")

   [Environment]::SetEnvironmentVariable("DOCKER_MACHINE_NAME", $null, "User")

   [Environment]::SetEnvironmentVariable("DOCKER_TLS_VERIFY", $null, "User")

   [Environment]::SetEnvironmentVariable("DOCKER_TOOLBOX_INSTALL_PATH", $null, "User")

5. Restart PowerShell. (If necessary, restart system as well.)

Sources:

• Fresh install - could not read CA certificate. The system cannot find the path specified.

• [Docker for Windows] Certificate Error Solution

Answer 2

Environment variables hanging around from previously (long) removed Docker Toolbox installation caused this problem with Docker Desktop (which was started ok after HyperV. Removed them all, remove these environmental variables

• DOCKER_TLS_VERIFY
• DOCKER_CERT_PATH
• DOCKER_HOST
• DOCKER_TOOLBOX_INSTALL_PATH

, restart terminal, all working great now