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[Launchpad Bug Tracker <1720109@xxxxxxxxxxxxxxxxxx>]

This bug was fixed in the package net-snmp - 5.7.3+dfsg-1ubuntu4.1

---------------
net-snmp (5.7.3+dfsg-1ubuntu4.1) xenial; urgency=medium

  * d/snmpd.init: also match start-stop-daemon against pidfile to avoid
    killing extra snmpd processes for example in container (LP: #1720109)

 -- Christian Ehrhardt <christian.ehrhardt@xxxxxxxxxxxxx>  Tue, 20 Feb
2018 14:53:51 +0100

** Changed in: net-snmp (Ubuntu Xenial)
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1720109

Title:
  snmpd stop on host stops snmpd on LXD containers

Status in net-snmp package in Ubuntu:
  Fix Released
Status in net-snmp source package in Xenial:
  Fix Released

Bug description:
  [Impact]

   * Stopping snmpd in Xenial can stop container processes of the same 
     binary

   * Fix by matching to the PIDFILE that is already tracked by snmpd

  [Test Case]

   * Set up a host (e.g. a VM being Xenial)
   * Set up at least one (or more) containers in it
   * Install and start snmpd in the Host
   * Install and start snmpd in the containers
   * you'll now see like:
      root@ubuntu-vm:/var/log# ps fxaw|grep snmp
      29382 ? S 0:00 \_ /usr/sbin/snmpd -Lsd -Lf /dev/null -u snmp -g snmp    
      29308 ? S 0:00 /usr/sbin/snmpd -Lsd -Lf /dev/null -u snmp -g snmp 
    # One of these is from the container
   * now on the host stop your service, chances are you stop your guests instead
     root@ubuntu-vm:/var/log# service snmpd stop
     root@ubuntu-vm:/var/log# ps fxaw|grep snmp
     29426 pts/0 S+ 0:00 \_ grep --color=auto snmp
     # 29382 was from a lxd container in this case

  [Regression Potential]

   * In case the pidfile stored by the snmpd daemon would be incorrect then 
     the stop/restart actions would not match the process and fail to 
     stop/restart. We didn't see that in our tests, but that is the 
     regression I could think of.

  [Other Info]
   
   * n/a

  
  ----

  
  If you have ubuntu 16.04 containers running snmpd and you stop the snmpd on the LXD host system, it will also shut down all the snmpd instances on the containers (but will not restart them if you restart them on the LXD host) .. in fact, you even need to go back into the container, stop the snmpd before you can start it again.

  See log below, viepovzat17 is the LXD host, viezmaaat10 is the ubuntu
  container:

    driver: lxc
    driver_version: 2.0.8
    kernel: Linux
    kernel_architecture: x86_64
    kernel_version: 4.4.0-87-generic
    server: lxd
    server_pid: 4426
    server_version: "2.16"
    storage: zfs
    storage_version: 0.6.5.6-0ubuntu16

  root@viezmaaat10:~# /etc/init.d/snmpd start
  [ ok ] Starting snmpd (via systemctl): snmpd.service.
  root@viezmaaat10:~# ps -eaf | grep snmp
  snmp      1271     1  0 10:50 ?        00:00:00 /usr/sbin/snmpd -Lsd -Lf /dev/null -u snmp -g snmp -I -smux mteTrigger mteTriggerConf -p /run/snmpd.pid
  root      1291   757  0 10:50 ?        00:00:00 grep --color=auto snmp
  root@viezmaaat10:~#
  root@viezmaaat10:~# ps -eaf | grep snmp
  snmp      1271     1  0 10:50 ?        00:00:00 /usr/sbin/snmpd -Lsd -Lf /dev/null -u snmp -g snmp -I -smux mteTrigger mteTriggerConf -p /run/snmpd.pid
  root      1293   757  0 10:50 ?        00:00:00 grep --color=auto snmp
  root@viezmaaat10:~# exit

  root@viepovzat17:~# ps -eaf | grep snmp
  snmp     22757     1  0 10:45 ?        00:00:00 /usr/sbin/snmpd -Lsd -Lf /dev/null -u snmp -g snmp -I -smux mteTrigger mteTriggerConf -p /run/snmpd.pid
  100116   24118  5222  0 10:50 ?        00:00:00 /usr/sbin/snmpd -Lsd -Lf /dev/null -u snmp -g snmp -I -smux mteTrigger mteTriggerConf -p /run/snmpd.pid
  root     24153 21842  0 10:50 pts/1    00:00:00 grep --color=auto snmp
  root@viepovzat17:~# /etc/init.d/snmpd stop
  [ ok ] Stopping snmpd (via systemctl): snmpd.service.
  root@viepovzat17:~# ps -eaf | grep snmp
  root     24286 21842  0 10:50 pts/1    00:00:00 grep --color=auto snmp
  root@viepovzat17:~#

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