[Bug 1551855] Re: [xenial] systemctl hangs when stopping isc-dhcp-server

[Jamie Strandboge]

*** This bug is a duplicate of bug 1551351 ***
    https://bugs.launchpad.net/bugs/1551351

** This bug has been marked a duplicate of bug 1551351
   dhclient does not renew leases

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Title:
  [xenial] systemctl hangs when stopping isc-dhcp-server

Status in isc-dhcp package in Ubuntu:
  Confirmed

Bug description:
  This affects both 4.3.3-5ubuntu8 that exists in xenial right now and
  4.3.3-5ubuntu9 which I just uploaded to fix another bug.

  With the move to systemd service file, 'sudo systemctl stop isc-dhcp-
  server.service' just hangs. Here is the service file (from
  4.3.3-5ubuntu9):

  [Unit]
  Description=ISC DHCP IPv4 server
  Documentation=man:dhcpd(8)
  Wants=network-online.target
  After=network-online.target
  After=time-sync.target
  ConditionPathExists=/etc/default/isc-dhcp-server
  ConditionPathExists=|/etc/ltsp/dhcpd.conf
  ConditionPathExists=|/etc/dhcp/dhcpd.conf

  [Service]
  EnvironmentFile=/etc/default/isc-dhcp-server
  RuntimeDirectory=dhcp-server
  # The leases files need to be root:dhcpd even when dropping privileges
  ExecStart=/bin/sh -ec '\
      CONFIG_FILE=/etc/dhcp/dhcpd.conf; \
      if [ -f /etc/ltsp/dhcpd.conf ]; then CONFIG_FILE=/etc/ltsp/dhcpd.conf; fi; \
      [ -e /var/lib/dhcp/dhcpd.leases ] || touch /var/lib/dhcp/dhcpd.leases; \
      chown root:dhcpd /var/lib/dhcp /var/lib/dhcp/dhcpd.leases; \
      chmod 775 /var/lib/dhcp ; chmod 664 /var/lib/dhcp/dhcpd.leases; \
      exec dhcpd -user dhcpd -group dhcpd -f -4 -pf /run/dhcp-server/dhcpd.pid -cf $CONFIG_FILE $INTERFACES'

  [Install]
  WantedBy=multi-user.target

  
  Eg:
  $ sudo systemctl stop isc-dhcp-server.service
  <hangs>

  wait long enough and systemd will KILL it. In the logs:
  Mar  1 10:58:14 sec-xenial-amd64 systemd[1]: isc-dhcp-server.service: State 'stop-sigterm' timed out. Killing.
  Mar  1 10:58:14 sec-xenial-amd64 systemd[1]: isc-dhcp-server.service: Main process exited, code=killed, status=9/KILL
  Mar  1 10:58:14 sec-xenial-amd64 systemd[1]: isc-dhcp-server.service: Unit entered failed state.
  Mar  1 10:58:14 sec-xenial-amd64 systemd[1]: isc-dhcp-server.service: Failed with result 'signal'.

  
  Things I tried to resolve it, none of which worked:
   * add Type=forking
   * add Type=forking and remove '-f' from the dhcpd exec
   * adjust /run/dhcp-server to be root:root and 755
   * adjust /run/dhcp-server to be dhcpd:dhcpd and 755 (this was in 4.3.3-5ubuntu8 but fails to create a pid file and was fixed in 4.3.3-5ubuntu9)
   * adjust /run/dhcp-server to be root:dhcpd and 775
   * add Type=forking and remove '-f' from the dhcpd exec and use KillSignal=SIGINT (see https://wiki.archlinux.org/index.php/Dhcpd#Service_file)

  
  This bug is not related to AppArmor. With 4.3.3-5ubuntu9 this bug persists and there are no apparmor denials. Furthermore, if I disable the apparmor profile, the bug persists.

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