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Can someone explain this:

These are the commands inside a CC7 based container running on Centos6.

[cmsbuild@f6c45f375b0e build]$ cat /etc/system-release
CentOS Linux release 7.2.1511 (Core) 
[cmsbuild@f6c45f375b0e build]$ uname -a
Linux f6c45f375b0e 2.6.32-642.11.1.el6.x86_64 #1 SMP Wed Nov 16 09:40:09   CET 2016 x86_64 x86_64 x86_64 GNU/Linux

Why is there an el6 in the uname command output? Is it comming from the host system?

1 Answer 1

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Yes, it reports the kernel version, which is running on your host. The containers share the kernel with the host, not like a virtual machine.

Rather than consider containers like virtual machines, consider that it is just a process or group of processes that have a set of isolated name spaces:

  • filesystem
  • network stack
  • user ids
  • and more

Even if your container filesystem included a kernel it wouldn't be loaded, the system libraries in the container process talk to the existing running kernel.

The uname binary calls the uname() system call which talks directly to the kernel, it does not look at any files on the file system

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