Processes scope and visibility

This HOWTO shows how OpenVZ hardware node administrator can see a processes belonging to the host system only, or to a particular container.

Problem

From CT0 one can see all the processes running on the system; that includes all the processes of all containers and the processes of the host system itself. Sometimes you just want to see the processes from the host system only. Sometimes you just want to see the processes from a particular container.

There are many ways to achieve it.

Solutions

Hide container processes from host completely

It is possible to hide other CT's processes from CT0. For this just enable kernel.pid_ns_hide_child sysctl parameter:

sysctl -w 'kernel.pid_ns_hide_child=1'

and restart all containers. To make setting permanent put into /etc/sysctl.conf following line:

kernel.pid_ns_hide_child=1

After this ps or htop or top will not show other container processes.

Warning: If you use checkpointing and/or live migration, note they are not compatible with this feature and will stop working.

"Poor man's vzps in bash"

Use the following script by aistis, broken by Kir, fixed by Hvdkamer.

First argument is CT ID (0 for the host system), all the remaining arguments are passed to ps(1) utility.

#!/bin/bash
# Usage: ./ovzps CTID [ps flags ...]

function find_container_pids(){
       local pid
       local myctid=$1
       local ctpids=

       for pid in $ALLPIDS; do
               [ -f /proc/$pid/status ] || continue
               ctid=`grep envID /proc/$pid/status | awk -F: '{print $2}'`
               if [ ${ctid} = ${myctid} ]; then
                       ctpids="$ctpids $pid"
               fi
       done
       echo "$ctpids"
}

ALLPIDS=`ps -A -o pid --no-headers`
CTPIDS=`find_container_pids $1`
shift

if [ -n "${CTPIDS}" ]; then
        ps $* -p $CTPIDS
else
        exit 0
fi

A faster version:

#! /bin/bash
# Usage: ovzps <CTID> [ps flags ...]

ctid=${1:-0}
shift

ps $* -p $(grep -l "^envID:[[:space:]]*$ctid\$" /proc/[0-9]*/status | 
	sed -e 's=/proc/\([0-9]*\)/.*=\1=')

Use vzprocps tools

Take vzprocps tools from http://download.openvz.org/contrib/utils/. These are usual ps and top utilities (named vztop and vzps to not conflict with the standard ones) with an -E option added. You can use -E CTID option to limit the output to the selected CTID (use 0 for the host system), or just -E without an argument to just add CTID column to output.

Use vzprocps-perl tools

Take vzprocps-perl tools from http://sourceforge.net/p/vzprocpsperl/wiki/vzprocps-perl/. Write in Perl with basics functions. Can be used in x86_64 architecture.

See also

• Forum thread #836