[lxc-users] Error: /proc must be mounted

[Itamar Gal]

Dear lxc-users,

First I will give an extremely brief description of my problem. I recently
upgrade some packages on my server. Containers which have been created since
the upgrade are having some issues. Specifically, if I run the ps command I get
the following error:

    $ ps

    Error: /proc must be mounted
      To mount /proc at boot you need an /etc/fstab line like:
          proc   /proc   proc    defaults
      In the meantime, run "mount proc /proc -t proc"

Now I will give more background and describe some of my attempts to further
investigate and resolve the issue.


I have a server running Ubuntu 12.04.5 LTS (Precise Pangolin). I recently
performed an upgrade of all system packages (i.e. apt-get upgrade) after not
having done so for some time. Here are the contents of my apt sources file:

    $ cat /etc/apt/sources.list

    # Standard packages
    deb http://us.archive.ubuntu.com/ubuntu/ precise main restricted
universe multiverse
    deb http://us.archive.ubuntu.com/ubuntu/ precise-updates main
restricted universe multiverse
    deb http://security.ubuntu.com/ubuntu precise-security main
restricted universe multiverse

    # PPA for virtual box
    deb http://download.virtualbox.org/virtualbox/debian precise contrib

In particular, this operation resulted in an upgrade of the kernel and of some
LXC-related packages. Here is some version information related to LXC:

    $ uname -a

    Linux myhostname 3.2.0-86-generic #124-Ubuntu SMP
    Wed Jun 17 21:40:14 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

    $ apt-show-versions | grep lxc

    liblxc1/precise uptodate 2.0.5+master~20161122-0513-0ubuntu1~precise
    lxc/precise uptodate 2.0.5+master~20161122-0019-0ubuntu1~precise
    lxc-common/precise uptodate 2.0.5+master~20161122-0513-0ubuntu1~precise
    lxc-templates/precise uptodate 2.0.5+master~20161122-0513-0ubuntu1~precise
    lxc1/precise uptodate 2.0.5+master~20161122-0513-0ubuntu1~precise
    lxcfs/precise uptodate 2.0.4-0ubuntu1~ubuntu12.04.1~ppa1
    lxctl/precise uptodate 0.3.1+debian-1
    python3-lxc/precise uptodate 2.0.5+master~20161122-0513-0ubuntu1~precise


Here is an example of how I might go about reproducing my problem. First I
create a container, start it and log in via the console:

    sudo lxc-create -n "temp-test" -t "ubuntu" -- --release "trusty"
    sudo lxc-start -n "temp-test"
    sudo lxc-console -n "temp-test"


Once inside the container, I try to run the ps command and follow some
instructions:

    $ ps

    Error: /proc must be mounted
      To mount /proc at boot you need an /etc/fstab line like:
          proc   /proc   proc    defaults
      In the meantime, run "mount proc /proc -t proc"


    $ sudo mount proc /proc -t proc

    mount: proc already mounted


    $ sudo ps

    Error: /proc must be mounted
      To mount /proc at boot you need an /etc/fstab line like:
          proc   /proc   proc    defaults
      In the meantime, run "mount proc /proc -t proc"


Then I check my fstab (it's empty):

    $ cat /etc/fstab

    # UNCONFIGURED FSTAB FOR BASE SYSTEM


Then I try an strace:

    $ strace ps aux 2>&1 | tail

    ioctl(1, SNDCTL_TMR_TIMEBASE or SNDRV_TIMER_IOCTL_NEXT_DEVICE or
TCGETS, 0x7ffc59676200) = -1 EINVAL (Invalid argument)
    geteuid()                               = 1000
    open("/proc/uptime", O_RDONLY)          = -1 ENOTCONN (Transport
endpoint is not connected)
    write(2, "Error: /proc must be mounted\n  T"..., 176Error: /proc
must be mounted
      To mount /proc at boot you need an /etc/fstab line like:
          proc   /proc   proc    defaults
      In the meantime, run "mount proc /proc -t proc"
    ) = 176
    exit_group(102)                         = ?


I try to google for the error:

    Transport endpoint is not connected

Unfortunately I was unable to find a solution that way. I also looked at the
lxcfs upstart log (on the host):

    $ sudo cat /var/log/upstart/lxcfs.log

    bindings.c: 4484: collect_and_mount_subsystems: Failed to preserve
initial mount namespace.

This lead to more fruitless google searches. I think that covers most of it.
I'm not sure how to proceed. Any help or advice would be greatly appreciated.

Cheers,
Itamar