[Bug 1543794] Re: isc-dhcp-server fails to start on second & further attempts with 'Can't open /var/lib/dhcp/dhcpd.leases for append'

[Rolly Ng]

Issue still exists with fresh installation of 16.04 server.

rolly at head:~$ apt-show-versions | grep isc-dhcp-server
isc-dhcp-server:amd64/xenial-updates 4.3.3-5ubuntu12.6 uptodate

it works with the solution:
sudo ln -s /etc/apparmor.d/usr.sbin.dhcpd /etc/apparmor.d/disable/
sudo apparmor_parser -R /etc/apparmor.d/usr.sbin.dhcpd

I am running dhcpd on infiniband, ipoib on ib0, here is the working output:
rolly at head:~$ sudo service isc-dhcp-server status
[sudo] password for rolly: 
● isc-dhcp-server.service - ISC DHCP IPv4 server
   Loaded: loaded (/lib/systemd/system/isc-dhcp-server.service; disabled; vendor preset: enabled)
   Active: active (running) since Mon 2017-01-09 22:05:34 HKT; 19min ago
     Docs: man:dhcpd(8)
 Main PID: 5173 (dhcpd)
    Tasks: 1
   Memory: 9.0M
      CPU: 25ms
   CGroup: /system.slice/isc-dhcp-server.service
           └─5173 dhcpd -user dhcpd -group dhcpd -f -4 -pf /run/dhcp-server/dhcpd.pid -cf /etc/dhcp/dhcpd.conf ib0

Jan 09 22:05:34 head dhcpd[5173]: All rights reserved.
Jan 09 22:05:34 head dhcpd[5173]: For info, please visit https://www.isc.org/software/dhcp/
Jan 09 22:05:34 head dhcpd[5173]: Wrote 0 leases to leases file.
Jan 09 22:05:34 head dhcpd[5173]: Listening on LPF/ib0//192.168.0.0/24
Jan 09 22:05:34 head sh[5173]: Listening on LPF/ib0//192.168.0.0/24
Jan 09 22:05:34 head sh[5173]: Sending on   LPF/ib0//192.168.0.0/24
Jan 09 22:05:34 head sh[5173]: Sending on   Socket/fallback/fallback-net
Jan 09 22:05:34 head dhcpd[5173]: Sending on   LPF/ib0//192.168.0.0/24
Jan 09 22:05:34 head dhcpd[5173]: Sending on   Socket/fallback/fallback-net
Jan 09 22:05:34 head dhcpd[5173]: Server starting service.

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https://bugs.launchpad.net/bugs/1543794

Title:
  isc-dhcp-server fails to start on second & further attempts with
  'Can't open /var/lib/dhcp/dhcpd.leases for append'

Status in isc-dhcp package in Ubuntu:
  Fix Released

Bug description:
  During the first start of isc-dhcp-server (using the systemd service
  unit), a blank dhcpd.leases file is created (presumably owned by
  root:root).  dhcpd starts successfully (and then exits due to no
  subnet definitions, that's expected).

  Attempting to start the service again fails with 'Can't open
  /var/lib/dhcp/dhcpd.leases for append' (the dhcpd.leases file
  ownership is now dhcpd.dhcpd), and apparmor logs a denial of the
  dac_override capability.

  Removing the leases file repeats this process (first start works as
  expected, future ones do not).

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: isc-dhcp-server 4.3.3-5ubuntu4
  ProcVersionSignature: Ubuntu 4.4.0-2.16-generic 4.4.0
  Uname: Linux 4.4.0-2-generic x86_64
  ApportVersion: 2.19.4-0ubuntu2
  Architecture: amd64
  Date: Tue Feb  9 20:58:12 2016
  InstallationDate: Installed on 2016-02-09 (0 days ago)
  InstallationMedia: Ubuntu-Server 16.04 LTS "Xenial Xerus" - Alpha amd64 (20160206)
  ProcEnviron:
   LANGUAGE=en_GB:en
   TERM=linux
   PATH=(custom, no user)
   LANG=en_GB.UTF-8
   SHELL=/bin/bash
  SourcePackage: isc-dhcp
  UpgradeStatus: No upgrade log present (probably fresh install)

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