Network Namespace Creation Failure

Problem Description

The command for creating a network namespace got stuck and did not continue. dmesg message: "unregister_netdevice: waiting for lo to become free. Usage count = 1"

Cause of the Problem

It is caused by a bug of the kernel.
The following kernel versions have this bug:

• Ubuntu 16.04 x86_64 kernel version: 4.4.0-91-generic.
• Ubuntu 16.04 x86_32 kernel version: 4.4.0-92-generic.

Solution

Upgrade the kernel version to 4.4.0-98-generic, in which the bug has been fixed.

Procedure

1. Check the current kernel version.

   uname -r

2. Check whether version 4.4.0-98-generic is available for upgrade.

   sudo apt-get update
   sudo apt-cache search linux-image-4.4.0-98-generic

   If the following information is shown, it means the version to upgrade to exists in the source:

   linux-image-4.4.0-98-generic - Linux kernel image for version 4.4.0 on 64 bit x86 SMP

3. Install the new version kernel and corresponding Header package.

   sudo apt-get install linux-image-4.4.0-98-generic linux-headers-4.4.0-98-generic

4. Restart the system.

   sudo reboot

5. Enter the system to check the kernel version.

   uname -r

   If the following result is displayed, it means the version upgrade is successful:

4.4.0-98-generic