Stopping DHCPv6 client: invoke-rc.d: initscript dibbler-client, action "stop" failed.

[Amos Jeffries]

Upgrade to Natty fails with:
"
Preparing to replace dibbler-client 0.7.3-1.1 (using .../dibbler-client_0.7.3-1.3_i386.deb) ...
Stopping DHCPv6 client: invoke-rc.d: initscript dibbler-client, action "stop" failed.
dpkg: warning: subprocess old pre-removal script returned error exit status 1
dpkg - trying script from the new package instead ...
Stopping DHCPv6 client: invoke-rc.d: initscript dibbler-client, action "stop" failed.
dpkg: error processing /var/cache/apt/archives/dibbler-client_0.7.3-1.3_i386.deb (--unpack):
 subprocess new pre-removal script returned error exit status 1
No apport report written because MaxReports is reached already
                                                              Errors were encountered while processing:
 /var/cache/apt/archives/dibbler-client_0.7.3-1.3_i386.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)
"

After much digging I re-discover a bug I thought was resolved with Feisty Fawn...
"
/usr/sbin/dibbler-client run
| Dibbler - a portable DHCPv6, version 0.7.3 (CLIENT, Linux port)
| Authors : Tomasz Mrugalski<thomson(at)klub.com.pl>,Marek Senderski<msend(at)o2.pl>
| Licence : GNU GPL v2 only. Developed at Gdansk University of Technology.
| Homepage: http://klub.com.pl/dhcpv6/
2011.05.09 22:54:54 Client Warning Pid file found (pid=829, file /var/lib/dibbler/client.pid), but process 829 does not exist.
2011.05.09 22:54:54 Client Notice My pid (7866) is stored in /var/lib/dibbler/client.pid
"

Two problems;
 1) superficially the location of PID file in /var/lib instead of /var/run is a violation of the FHS standards and difficult for administrators to track down.
 2) worse, is that this file containing errors is fatal to dibbler-client. "stop" command should recover from the absence of a running binary by reporting none running and a *clean* exit. Not just silence with an error exit.

This is not the end of the story though. The workaround found previously now fails as well:
"
~#/usr/sbin/dibbler-client stop
| Dibbler - a portable DHCPv6, version 0.7.3 (CLIENT, Linux port)
| Authors : Tomasz Mrugalski<thomson(at)klub.com.pl>,Marek Senderski<msend(at)o2.pl>
| Licence : GNU GPL v2 only. Developed at Gdansk University of Technology.
| Homepage: http://klub.com.pl/dhcpv6/
Attaching to process 8525 failed: No such process
Warning: Can not guarantee for remote process termination
Sending TERM signal to process 8525
Signal sending failed: No such process
~# ps aux | grep 8525
~# rm /var/lib/dibbler/client.pid ; touch /var/lib/dibbler/client.pid
~# /usr/sbin/dibbler-client stop
| Dibbler - a portable DHCPv6, version 0.7.3 (CLIENT, Linux port)
| Authors : Tomasz Mrugalski<thomson(at)klub.com.pl>,Marek Senderski<msend(at)o2.pl>
| Licence : GNU GPL v2 only. Developed at Gdansk University of Technology.
| Homepage: http://klub.com.pl/dhcpv6/
Attaching to process 4 failed: No such process
Warning: Can not guarantee for remote process termination
Sending TERM signal to process 4
Signal sending failed: No such process

"
... and no change...

~# aptitude upgrade
...
Preparing to replace dibbler-client 0.7.3-1.1 (using .../dibbler-client_0.7.3-1.3_i386.deb) ...
Stopping DHCPv6 client: invoke-rc.d: initscript dibbler-client, action "stop" failed.
dpkg: warning: subprocess old pre-removal script returned error exit status 1
dpkg - trying script from the new package instead ...
Stopping DHCPv6 client: invoke-rc.d: initscript dibbler-client, action "stop" failed.
dpkg: error processing /var/cache/apt/archives/dibbler-client_0.7.3-1.3_i386.deb (--unpack):
 subprocess new pre-removal script returned error exit status 1
Errors were encountered while processing:
 /var/cache/apt/archives/dibbler-client_0.7.3-1.3_i386.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)