      Popularity-contest Frequently Asked Questions.

Q) What informations are reported by popularity-contest ?

A) popularity-contest report the Debian architecture you use, the version of
   popularity-contest you use and the list of packages installed on your
   system. For each packages, popularity-contest looks at the most recently
   used (based on atime) files, and report the filename, its last access time
   (atime) and last change time (ctime). However, some files are not considered,
   because they have unreliable atime.

Q) What are the privacy consideration for popularity-contest ?

A) Each popularity-contest host is identified by a random 128bit uuid
   (MY_HOSTID in /etc/popularity-contest.conf). This uuid is used to track
   submission issued by the same host. It should be kept secret.  The reports
   are sent by email to the popcon server.  The server automatically extract
   the report from the email and store it in a database for a maximum of 20
   days or until the host send a new report. This database is readable only by
   Debian Developers.  The emails are readable only by the server admins.
   Every day, the server compute a summary and post it on
   <http://popcon.debian.org/all-popcon-results.txt.gz>. This summary is a
   merge of all the submissions and does not include uuids.
   
   Known weakness of the system:
   
   1) Your email submission might be intercepted. We evaluate the possibility
   to use public-key cryptography to protect the email.
   
   2) Someone who know you are very likely to use a particular package reported
   by only one person (e.g. you are the maintainer) might infer you are not at
   home when the package is not reported anymore. However this is only a
   problem if you are gone for more than two weeks if the computer is shut-down
   and 23 days if it is let idle.  
   
   3) Unofficial and local packages are reported. This can be an issue
   especially with 2) above, especially for custom-build kernel packages.
   We are evaluating how far we can alleviate this problem.
   
Q) My submissions bounce with 
   550 [PERMFAIL] popcon.debian.org requires valid sender domain.

A) popularity-contest send the report as root but the email address of the root
   user was not configured properly. With exim, you can add an entry for root
   in /etc/email-addresses with a suitable address.

   A better fix would be to change popcon.debian.org to not reject emails with
   invalid sender domain in the first place, but it is out of our reach for the
   time being.

Q) /usr is mounted with 'noatime'.

A) popularity-contest relies on atime to know what packages were used during
   the last month. This means you will only report the list of packages
   installed without usage information.

Q) When does popularity-contest run ?

A) popularity-contest is run by the weekly cron job 
/etc/cron.weekly/popularity-contest.
Under the default configuration of cron, this happens every sundays
at 6:47 in the morning. This can be changed by editing /etc/crontab
but if your computer is not always turned on, we really recommend you
install the anacron package.

Q) I don't want popcon email to be send by root! How can I send that ?

A) To send as user 'myuser', edit the function 'do_sendmail' in
/etc/cron.weekly/popularity-contest to 

do_sendmail()
{
  su myuser -s /bin/sh -c "/usr/sbin/sendmail -oi \"$MAILTO\""
}

Make sure myuser account is properly configured to send email with a valid
return address.


