[lxc-users] Unable to fork - LXD process limit?

[Phillips, Julian]

It appears that the issue was due to the centos image imposing a 1024 softlimit on the number of processes.  I wouldn't expect limits configured inside a container to cause affects across containers, but at least I have been able to increase the limit in all the containers and can now run as many processes as needed.

From: Phillips, Julian
Sent: 14 June 2017 10:36
To: LXC users mailing-list
Subject: RE: [lxc-users] Unable to fork - LXD process limit?

It's 1024 total across all containers.  Yesterday I was able to cause the same problem with only two containers (both CentOS 6.8 un-customized).  I started 1024 processes in container 2, and was unable to run "su - user" in container 1.  The only thing I did to the host after install was to update to 16.04.2 (install image was 16.04).

(sorry for top posting ...)

From: lxc-users [mailto:lxc-users-bounces at lists.linuxcontainers.org] On Behalf Of Stéphane Graber
Sent: 13 June 2017 16:05
To: LXC users mailing-list
Subject: Re: [lxc-users] Unable to fork - LXD process limit?

On Tue, Jun 13, 2017 at 08:56:25AM +0000, Phillips, Julian wrote:
> Hello,
>
> I'm trying to setup LXD (2.0.9) on Ubuntu 16.04 to run 32 Centos 6 containers, but I seem to be running into a process limit?
>
> After building the containers, if I run "lxc exec container -- su - user" then I get "can not fork user shell: Resource temporarily unavailable". The only thing I can see that might be related is that /sys/fs/cgroups/pids/lxc/pids.current is a bit over 1024, which sounds like I might be hitting a 1024 limit. However /sys/fs/cgroups/pids/lxc/pids.max is "max", and I don't know what else might apply. Does anyone know if there is a limit I need to change somewhere to allow LXD to run more than 1024 processes at once?
>
> Yours hopefully,
> Julian

With 32 containers at 1024 processes, that's 32k which is the global
pidmax for most Linux distributions.

You may want to bump the value in /proc/sys/kernel/pid_max on the host
to something significantly larger than its current value.


--
Stéphane Graber
Ubuntu developer
http://www.ubuntu.com<http://www.ubuntu.com>

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