No Internet access from your Docker container? Check this out!

After a recent update I started having issues with my containers that hosted apps which were accessing the outside world periodically. At first I couldn’t understand where the problem is. I’ve been checking a lot Github issues without success and finally I remembered that I’ve made an update to my host which updated the kernel.

What I needed now is to find a way to boot with an older kernel selected by default. I started looking in Stackoverflow pages and blogs and found a way to set any kernel that I already have installed as the default one.

Here are the steps I took to fix my problem(my host is running Ubuntu linux):

  • check the /boot/grub/grub.cfg file for all available options you have. The name of every kernel installed is there. Pick one that is older than the latest installed. You have to look for entries like: “menuentry ‘Ubuntu, with Linux 3.13.0-113-generic'”. You will use the “Ubuntu, with Linux 3.13.0-113-generic” part
  • next open the /etc/default/grub file and look for the GRUB_DEFAULT entry
  • combine your kernel config name from point one from above with “Advanced options for Ubuntu” or “Previous Linux versions” for older Ubuntu versions (<14.04). You’ll have to have a similar string like this one now: “Previous Linux versions>Ubuntu, with Linux 3.13.0-92-generic”. Set GRUB_DEFAULT to this string like: GRUB_DEFAULT=Previous Linux versions>Ubuntu, with Linux 3.13.0-92-generic
  • you can use numeric values for GRUB_DEFAULT but it’s not recommended as the number will point to a random kernel config after the next update
  • save, run sudo update-grub and restart

Now you should have an Internet access from inside the Docker containers. This is just a temporary solution so don’t leave it like this, especially running with an older kernel. Better check you configuration and even reinstall everything on your host, use a newer linux distro, etc.

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About Iliyan Trifonov

Web Developer, Blogger
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