Unprivileged LXC container does not start with step by step usage instructions

[Andreas]

Following the steps in https://help.ubuntu.com/lts/serverguide/lxc.html#lxc-basic-usage might not work for the unprivileged container creation on a fresh Ubuntu 16.04.01 installation.

Depending on your initial installed packages, it might be required to open a new shell, otherwise the "lxc-start -n u1 -d" step might fail.

Some text as per Serge's comment #6 below should be added to clarify this possible requirement.

[Doug Smythies (dsmythies)]

I tested that exact area of the documentation on a brand new 16.04 server VM during the 16.04 cycle, and it worked fine. As far as I have been able to determine the package cgmanager is installed by default on a new sever, so we need to figure out what is different between our two installs.

[Andreas (0-andreas)]

I tried it again: I seems to work with 16.04 but not with 16.04 and a apt-get update && apt-get upgrade or 16.04.1.
After apt-get install cgmanager and a reboot everything works normal.

screen.log shows the part before the reboot.

[Doug Smythies (dsmythies)]

@Serge: I subscribed you to this bug report. I wonder if you could comment. Should the lxc package have a dependency on the cgmanager package? It doesn't appear to at the moment (but I did follow every dependency path from lxc1).

[Serge Hallyn (serge-hallyn)]

(Argh, web interfaces make me cranky. ctrl-w closed my lengthy comment)

In x and y lxc uses lxcfs, cgmanager is not needed.

in t lxcfs is only available in backports, so without backports cgmanager would be required.

[Doug Smythies (dsmythies)]

@Serge: Thanks, and note that we are only takling about "x" herein.

@Andreas: It seems to work fine for me. I did everything twice using:

699400192 Aug 13 10:34 ubuntu-16.04.1-server-amd64.iso

downloaded yesterday, and creating a brand new VM with it.

However, I also got the "failed to start" message at this step:

lxc-start -n u1 -d

but it worked fine after I re-booted, having done nothing else. In particular I do not have the cgmanager package installed:

doug@serv-dev:~$ dpkg -l | grep cgm
doug@serv-dev:~$

[Serge Hallyn (serge-hallyn)]

Note that (with or without cgmanager) you need a login shell with freezer and systemd cgroups delegated to you. If you did not have lxcfs or libpam-cgfs installed when you first logged in, you need to log back in, or open a new shell. Rebooting obviously also works.

[Andreas (0-andreas)]

I can confirm. It works fine after a logout and login. Cgmanager is not required.