Comment 9 for bug 809210

Verified with landscape-client-11.07.1.1-0ubuntu0.10.04.0 from lucid-proposed:

root@ls1-lucid:/var/lib/landscape/client# apt-cache policy landscape-client
landscape-client:
  Installed: 11.07.1.1-0ubuntu0.10.04.0
  Candidate: 11.07.1.1-0ubuntu0.10.04.0
  Version table:
 *** 11.07.1.1-0ubuntu0.10.04.0 0
        500 http://us.archive.ubuntu.com/ubuntu/ lucid-proposed/main Packages
        100 /var/lib/dpkg/status
     11.02-0ubuntu0.10.04.1 0
        500 http://security.ubuntu.com/ubuntu/ lucid-updates/main Packages
     1.5.0.1-0ubuntu0.10.04.0 0
        500 http://us.archive.ubuntu.com/ubuntu/ lucid/main Packages

I made sure the old file had valid content and corrupted the main one. Then restarted landscape-client. The old file was used correctly, and the client continued working normally and was still registered with the landscape server:

root@ls1-lucid:/var/lib/landscape/client# /etc/init.d/landscape-client stop
 * Stopping landscape-client daemon [ OK ]
root@ls1-lucid:/var/lib/landscape/client# cp broker.bpickle broker.bpickle.old
root@ls1-lucid:/var/lib/landscape/client# > broker.bpickle
root@ls1-lucid:/var/lib/landscape/client# l broker.bpickle*
-rw------- 1 landscape landscape 0 2011-07-27 21:57 broker.bpickle
-rw------- 1 landscape landscape 865 2011-07-27 21:57 broker.bpickle.old
root@ls1-lucid:/var/lib/landscape/client# /etc/init.d/landscape-client start
 * Starting the landscape-client daemon [ OK ]
root@ls1-lucid:/var/lib/landscape/client# l broker.bpickle*
-rw------- 1 landscape landscape 865 2011-07-27 21:58 broker.bpickle
-rw------- 1 landscape landscape 0 2011-07-27 21:57 broker.bpickle.old
root@ls1-lucid:/var/lib/landscape/client#

root@ls1-lucid:/var/lib/landscape/client# tail /var/log/landscape/broker.log -n 4
2011-07-27 21:59:10,086 INFO [MainThread] Starting urgent message exchange with https://staging.landscape.canonical.com/message-system.
2011-07-27 21:59:11,511 INFO [Dummy-1 ] Sent 13486 bytes and received 150 bytes in 1.42s.
2011-07-27 21:59:11,516 INFO [MainThread] Switching to normal exchange mode.
2011-07-27 21:59:11,518 INFO [MainThread] Message exchange completed in 1.43s.